Nutritional Secondary Hyperparathyroidism in the Horse

Pathologia Veterinaria 

Online 

http://vet.sagepub.com/ 

Nutritional Secondary Hyperparathyroidism in the Horse: With a Description of the 

Normal Equine Parathyroid Gland 

Lennart Krook and John E. Lowe 

Pathol Vet 1964 1: 1 

DOI: 10.1177/030098586400101s01 

The online version of this article can be found at: 

http://vet.sagepub.com/content/1/1_suppl/1 

Published by: 

http://www.sagepublications.com 

On behalf of: 

American College of Veterinary Pathologists 

Additional services and information for Pathologia Veterinaria Online can be found at: 

Email Alerts: http://vet.sagepub.com/cgi/alerts 

Subscriptions: http://vet.sagepub.com/subscriptions 

Reprints: http://www.sagepub.com/journalsReprints.nav 

Permissions: http://www.sagepub.com/journalsPermissions.nav 

Downloaded from 

vet.sagepub.com by guest on April 14, 2010

From the Department of Pathology and Bacteriology 

New York State Veterinary College 

Cornell University, Ithaca, N.Y. 

(Head: Professor P. OLAFSON) 

Nutritional Secondary 

Hyperparathyroidism in the Horse 

With a Description of the Normal Equine Parathyroid Gland 

LENNART KROOK and JOHN E. LOWE 

With 40 figures and 26 tables 

19 64 

BASEL (Switzerland) S. KARGER NEW YORK 



Supplementum ad Vol. 1 (1964) 

Pathologia Veterinaria 

International Journal of Vcterinary Pathology - Internationale Zeitschrift fur 

Vcterinarpathologic 

Editors: P. CoIiRs, Hannover - L. 2. SAUNDDRS, Philadelphia, Pa. 

S. Karger AG, Arnold-Bocklin-Strasse 25, Basel (Schweiz) 

All rights, including that of translation into foreign languages, reserved. 

Photomechanic reproduction (photocopy, microcopy) of this book or part of it without special 

permission of the publishers is prohibited. 

Copyright 1964 by S. Karger AG, Basel 

Printed in Switzerland by Brin i- Tanner AG, Basel 

Cliches: Aberegg-Steiner, Bern 



Contents 

Introduction and Ohjcct of Investigation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 

..... 

..... 

..... 

a) Review of thc literature . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ..... 

b) Present investigation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ..... 

3. The microscopic anatomy of the equine parathyroid glands . . . . . ..... 

a) Review of the literature . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ..... 

b) Present investigation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ..... 

4. Discussion .. . . . . . . . . . . . .. . . . . . . .. . . . .. . . . . ... . . . . . . . . . . .. ..... 

I. The Anatomy of the Parathyroid Glands in the Horse . . . . . . . . , . . . . 

1. Comparative aspects of the embryology of the equine parathyroids 

2. The macroscopic anatomy of the equine parathyroid glands , . . . . 

II. NutritionalSecondary Hyperparathyroidism in the Horse: Revietv of the Literutzcre 

1. The nature of the osteopathy 

2. Etiology . .. . .. . . ... .._....... .. ......................... 

3. Occurrence and breed, sex, an 

4. Symptoms . . . . .. .. .. . . . .. . 

5. Clinical pathology . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 

6. Roentgenologic changes . . . . . . . . . . . . . . . . . 

7. The parathyroid glands . . . . . . . . . . . . . . . . . . . . . . . . . . 

........... 

........... 

III. Experimental Nutritional Secondary Hyperparatkyroidism in the Horse: 

Design of the Experiment . . . . . . . . . . . . . . . . . . . . 

2. Ration . . . . . . . . . . . . .................................. 

3. Physical examination . . . . . . ............................ 

6. Necropsy 

............... 

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 

I V, Experimental Nutritional Secondary Hyperparathyroidism in the Horse: 

Results . . ........................ 

1. Clinical observations . . . . . . . . . . . . . . . . . . . . . . . . . . . . 

2. Clinico-pathologic determinations . . . . . . . . . . . . . . . . . . 

........... 

3. Roentgenologic observations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 

4. Pathologic anatomy .................................. 


vet.sagepub.com by guest on April 14, 2010 

1 

3 

3 

5 

5 

6 

8 

8 

12 

24 

29 

29 

33 

35 

36 

36 

37 

38 

39 

39 

41 

41 

42 

42 

43 

44 

44 

46 

52 

57

V . Experimental Nritritional Secondary HJpcrparatLyroidism in the Horse: 

Discirssion ......................................... 

1 . Clinical course ..................................... ....... 71 

2 . Serum phosphorus. calcium and alkaline phosphatase ....... 

3 . Roentgenologic changes ........................................ 78 

4 . The parathyroid glands ..................................... 79 

5 . The skeleton .................................................. 81 

Siimnzay and Conclusions ............................................ 85 

References ........................................................ 88 

Appendix: Tables and Statistical Analyses ............................. 93 



Acknowledgements 

’I‘hc study reported in this thcsis was carricd out under National Institutes of 

Health Grant 26-213, “’The pathology of nutritional diseases”. The grant is 

gratefully ackiiowlcdgcd. 

The printing cost for this supplement was provided from “General Fund”, 

New York State Vcterinary College, for which the authors express their gratitude to 

the Dcan of the College, Dr. GEORGE C. POPPENSIEK. 

Dr. KAZUYA Usur of the university of Tokyo, Japan, once visiting professor 

at thc Dcpartlncnt of Pathology and Bacteriology, New York State Veterinary 

College, carried out the blood analyses. Dr. RICIIARD WARNER, professor of 

Animal Husbandry, Cornell University, ran the feed analyses and 1%. TIioMAs 

GREWELING, Dircctor of Laboratories, Cornell university, ran the water analyses. 

Their help has been much appreciated. 

The authors would like to express their gratitude to Dr. DONALD D. 

DELAIIANTY, New York State Veterinary College, for valuable suggestions and to 

Mr. GERALD RYAN for technical assistance regarding the radiographic examination. 

The authors also cxpress their gratitude to Dr. LEONARD BELANCER, 

profcssor of Histology and Embryology, School of Medicine, University of 

Ottawa, Canada, for many cnlightening discussions. 

Mr. VALEwrINE HANSEN, Supervisor of the animal quarters, Department of 

Pathology and Bactcriology, New York State Veterinary College, deserves our 

apprcciatioii for exccllcnt care of the horses. 

The authors want to thank Miss MARION NEWSON, Medical Illustrator, 

Ncw York State Veterinary College, for her illustrations (Figs. 1 and 2). 

Mr. HADT.EY SMrriI, Photographer, Ithaca, N. Y. and Mr. JOIIN BROCK, 

Photographcr, New York State Veterinary College, deserve our thanks for 

assista:ice with photography. 

‘The conscieritious tcchnical assistance of Mrs. JEAN MORROW, Mrs. PATRICIA 

WING, hfiss PRISCILLA MrNm and Mrs. I

Introduction and Object of Investigation 

Definitioiz. Nutritional secondary hyperparathyroidisin in the 

horse is a disease induced by the feeding of excessive amounts of 

phosphorus in proportion to calcium. The result is a depressed serum 

calcium level which acts as a stimulus to parathormone secretion, the 

end result being a generalized osteitis fibrosa. 

The subject of this treatise is one of the oldest known diseases of 

horses. .Yymp/omatic lerms applied to the condition include bighead, 

Kieferkl-ankbeit (German: “jaw disease”), and Cam itzchada (Spanish: 

“swollen face”). The multitude of morphologic terms used is impressive : 

osteomalacia, osteoporosis, osteitis fibrosa, cachexia osseus, halisteresis 

ostium, osteopsathyrosis, rarefying osteitis, osteitis deformans, osteitis 

fibrocystica, osteodystrophia fibrosa, osteodystrophia deformans, 

mollitis ossium, and fragilitas ossium. Etiologic terms, or at least ones 

suggesting the cause of the disease, have also been introduced, e. g. 

bran disease, millers’ disease, maladie dzi son (French : “bran disease”), 

Kleiekrankbeit (German : “bran disease”). 

Ideally a diagnosis should indicate etiology and pathogenesis, and, 

with this in mind, the following addition to the long list is suggested : 

nutritional secondary hyperparathyroidism. 

The clinical picture of the disease has been known for centuries. 

The true nature of the bone changes was uncovered in the early 1900’s. 

The etiology was discovered at the same time, and, as a result, adequate 

prophylactic and therapeutic measures were introduced. The patho- 

genesis, on the other hand, has not yet been elucidated. 

The object of the present investigation was: 

1. To study the anatomy of the parathyroid glands in normal 

horses and thus establish essential background data for an experimental 

study of nutritional secondary hyperparathyroidism ; 



2 Introduction and Object of Investigation 

2. To study the continuous changes in the phosphorus, calcium, 

and alkaline phosphatase levels in blood serum of horses suffering 

from experimental nutritional secondary hyperparathyroidism induced 

by imbalanced calcium-phosphorus feeding ; 

3. To study the continuous roentgenologic changes in the 

skeleton in nutritional secondary hyperparathyroidism of the horse ; 

and 

4. To study the morphology of experimental nutritional secondary 

hyperparathyroidism in the horse with special reference to the func- 

tional state of the parathyroid glands. 



I. The Anatomy of the Parathyroid Glands in the Horse 

1. Comparative Aspects of the Embryology of the Equine Parathyroids 

The anatomy of the parathyroids in the horse is different in many 

respects from that in other species. Interpretation of these differences 

requires appreciation of the embryologic development ; consequently 

this subject is briefly reviewed. 

The embryology of the pharyngeal region in man has been 

extensively studied [PISCHINGER (1937) and BARGMANN (1939) among 

others]. In man the parathyroid primorda appear in pharyngeal 

pouches I11 and IV, and, accordingly, the glands are called parathyroid 

I11 and parathyroid IV, respectively. In the third pouch 

the parathyroid primordium develops in close contact with the 

thymus and follows its descent for some distance. Separation does 

not occur until it has obtained a location distal to the parathyroid 

primordium of the fourth pouch. This topography remains postnatally, 

and the following terms are therefore used synonymously in 

man: parathyroid I11 or lower or external; parathyroid IV or upper 

or internal. 

In most other mammals the parathyroids are, similarly, derivatives 

of pharyngeal pouches I11 andIV GOD WIN(^^^^); PISCHINGER(~~~~); 

BARGMANN (1939)l. In some species, e.g., swine and rats, parathyroid 

primordia occur in the third pouch only. In mammals with parathyroid 

primordia in both pouches the embryologic development is different 

from that in man. It is true that the anlage of the third pouch descends 

with thymus I11 for a while, but thymus-parathyroid separation occurs 

before complex I11 has reached or surpassed the level of complex IV 

[GODWIN (1937) in the dog]. The original relationship between parathyroids 

111 and IV is therefore not reversed, and, as in all species, the 

niediolateral relationship is not changed. In the dog parathyroid I11 is 

therefore located at the dorsolateral aspect of the anterior end of the 



4 ‘The Anatomy of the Parathyroid Glands in the Horse 

thyroid, whereas parathyroid IV is usually located dorsomedially in the 

midsection of the thyroid. 

The literature on the embryology of the pharyngeal area in the horse 

is limited. The papers by EWART (1915) and ROBINSON and GIBSON 

(1915) do not specifically concern the parathyroids. Both papers, 

however, mention that in the horse the third pharyngeal pouch is 

much larger than the fourth. HARRISON and MOHN (1932) studied two 

horse embryos, 13 and 18 mm. in length. Parathyroid primordia were 

not observed in the smaller embryo. In the 18 mm. stage only one pair 

of parathyroids was identified, but the authors left the question of their 

derivation open. 

As will be described below, cysts occur very frequently around 

and within the equine parathyroid glands. GILMOUR (1937), in his 

description of the embryology of the pharyngeal pouches in man 

wrote: “They are rudimentary and of no apparent function but are 

important in that they persist into adult life and must be recognized if 

cystic structures in the neighbourhood of the parathyroids after birth 

are to be interpreted correctly.” The embryologic background of these 

cysts was first described by ~(URSTEINER (1899). He showed that a 

communicating segment between thymus I11 and parathyroid I11 

exists in all embryos. He referred to this as “gland canals” and “gland 

vesicles” (Driisenkade and Driiserzbla.rcben). In the human embryo 

these canals are best developed at the 20 cm. stage andusuallydisappear 

at the 30 cm. stage. In the newborn they are present at the hilus of the 

parathyroid gland only occasionally. They appear only in relation to 

parathyroid 111. ~(URSTEINER hypothesized that these canals, now 

usually associated with his name, may undergo cystic dilation and 

that they actually are responsible for congenital cysts in the upper 

cervical region. GILMOUR (1937) further studied these embryonic 

rudiments and recognized three types of canalicular, vesicular, or 

glandlike structures. Type I consists of small, solid, cellular buds 

originating from the parathyroid before the separation of thymus I11 

and parathyroid 111. A lumen may occur in the bud and a vesicle is thus 

formed. GILMOUR’S type 2 is a glandlike alveolus with a small lumen 

surrounded by cubical cells believed to be derivatives of the thymus or 

its cord. Type 3 consists of larger vesicles or canals lined by flat cells. 

They were shown to be of thymic or thymus cord origin. Any one of 

the three types may persist into adult life. In agreement with KUR- 

STEINER, GILMOUK stated that these rudiments appear in relation to 

parathyroid I11 only. 



Comparative Aspects of the Embryology of the Equine Parathyroids 5 

Embryonic rudiments in the equine parathyroid glands have been 

given little attention in the literature. ESTES (1907), in his series of 

125 parathyroids, observed cysts at the hilus in 18 cases (14%). The 

cysts were usually lobulated “as if several cysts were attached at a 

common origin”. ESTES further wrote : “Microscopically it is seen that 

the capsule of the parathyroid runs over the cyst and forms its capsule 

also. In this capsule one sometimes finds masses of what is apparently 

thymus tissue, raising the question as to whether the cysts may 

possibly have originated from the thymus rather than the parathyroid.” 

No cysts were found “in the parathyroid substance.” LITTY (1907) 

described the parathyroid glands of 12 normal horses without cysts 

and 2 cases with such cysts, which he classified as cystic degeneration. 

2. The Macroscopic Anatomy of the Equine Parathyroid Glands 

a) Review of the Literatwe 

SANus,rnoM (1880) dcscribcd om pair of parathyroid glaiids locatcd at thc 

anterior dorsolateral aspect of the thyroid artery. Es~es (1907) confirmed this pair 

and stated that the horsc has two pairs of parathyroid glands. After serial sectioning 

of the thyroid glands, ESTES claimcd to havc demonstratcd parathyroids within 

13 out of 25 thyroids. “They seem to bc distributed irregularly in the thyroid 

tissue, occurritig often iicar the superior pole in a rather superficial position 

but are sometimes dccplp cmbedded.” VT:RMEULEN (1917) stated that parathyroids 

I11 and IV reverse in thc horse, but he prescnted no embryologic evidence for 

his views. He callcd the larger, external gland parathyroid IV and further stated 

that in the horsc “all parathyroids arc always or in the majority of the cascs 

located externally.” 

In the work by Es.Ir.s and by VCRIVIHJLHN thc terms “cxtcrnally” aiid 

“internally” werc used to indicate the relationship to the thyroid gland rather than 

the cmbryologic origin. The discussion on the number of parathyroid glands in the 

horse was brought to an end by HAsIIIMwro and I

6 The Anatomy of the Parathyroid Glands in the Horse 

HASFIIMOTO and KATO (1932) used the terms “upper” and “lower” parathyroids. 

MEISSNIX (1958) and GRAU and DELLMAN (1958), in a rcview article, 

identified the lower parathyroid glands of HASIIIMOTO and I

The Aracroscopic Anatomy of the Equine Parathyroid Glands 

Fix. 1. Topography of upper parathyroid glands; summary of 36 cases. Each 

circle indicatcs the location of the gland on the left side. Dotted circles indicate 

location on the medial side of the structure. 

2.6 

2.4 

2.2 . 0 

2.0 . 

1.8 . 0 

1.6 . 

1.4 . 

1.2 . 0 

0.4 

0.2 . 

0 . 

0 

4 

+ + 

0 

0.1.2.3.4.5.6.7.8.9.10.1.12.13.14.15.16.17.18.19.20.21.2.23.24 

Chart I. Relative weight (mg per kg of body weight) of upper parathyroid glands 

in 36 normal horses. Weight on Y-axis, age in years on X-axis. o = male horses, 

+ = female horses. Solid line = rcgrcssion line of relative parathyroid weight as 

a function of age. 

0 



0 

0 

0 

7

8 ’The Anatomy of the Parathyroid Glands in the Horse 

Shape, sixe, and weight. The shape of the upper parathyroid was 

usually ellipsoidal; the long diameter averaged about 6 mm. in a 

medium-sized adult horse. Parathyroids in close contact with the 

thyroid were flattened and sometimes elongated with a beanshaped 

appearance. The relative weights, i. e., mg. of parathyroid per kg. of 

body weight, are given in Chart 1 (for analysis, see Appendix, Table I). 

The range in relative weight was great from horse to horse. The 

regression coefficient for parathyroid weights as a function of age was 

negative, but the decrease in weight with age was not significant. 

There were no relative weight differences between the sexes. 

Other macroscopic characteristics. The surface was coarsely or finely 

lobulated, seldom smooth. The color was light grayish brown. The 

cut surface was finely lobulated, slightly moist, and light grayish brown 

in color; sometimes it presented grossly visible cysts, which in rare 

instances reached a diameter of 10 mm. 

Lower Paratbroids 

Topograpb. The location of the lower parathyroids is summarized 

in Fig. 2. Glands located at the bifurcation of the truncus bicaroticus 

were all from young horses. The glands were located at the anterior 

pole of the thymus or were actually embedded in the thymus. Glands 

scattered along the trachea were often, almost as a rule, associated with 

a cystic thymus rudiment. 

Shape and sixe. The shape was usually ellipsoidal; the long dia- 

meter averaged 8 to 9 mm. in a medium-sized horse. Irregularly 

shaped glands occurred (Fig. 3). The lower glands were on the average 

twice as large as the upper ones (Fig. 4). Other macroscopic charac- 

teristics of the two pairs were identical. 

3. The Microscopic Anatomy of the Equine Parathyroid Glands 

a) Review of the Literature 

SANDSTR~M (1880) described briefly the histology of the equine parathyroid. 

He emphasized the fine lobulation of the gland in this species with epithelial cells 

irregularly packed together in acinuslike configuration. This is in contrast to the 

arrangement of the epithelial cells in anastomosing cords in most other mammalian 

species. The epithelial cells of equine parathyroids were, like those of the bovine, 

“somewhat larger than in man and have more protoplasm perhaps containing 

fine fat drops.” 



The Microscopic Anatomy of the Equine Parathyroid Glands 9 

Thy roi d gland 

.Bicarotid trunk 

Fig. 2. Topography of lower parathyroid glands; summary of 10 cases. Filled 

circles united with line indicate pair of parathyroid glaiids in one horse. Unfillcd 

circle from case in which only one gland was found. 




ESTES’ (1907) description clearly established that three main types of epithelial 

cells occur in the equine parathyroid, viz., chief cells, water-clear cells, and 

oxyphil cells. This should be emphasized in view of the fact that even modern 

textbooks and papers dealing with general parathyroid histology stress the 

existence of water-clear cells and oxyphil cells as a characteristic of the human 

parathyroid gland only. 

LITTY (1907) distinguished two types of epithelial cells in the equine parathyroid. 

In addition to the predominating light chief cells (according to modern 

nomenclature), he described large cells with well-defined borders, a clear cytoplasm, 

and a nucleus having variable staining properties. These cells usually 

occurred in restricted areas in small groups, but in rare cases they predominated 

in the microscopic field. 

BOBEAU (1911) contributed a detailed description of the histology of the 

equine parathyroids. He recognized four epithelial cell types, viz., light chief cells 

(celldes normales) with a longitudinal diameter of 12 to 16 p and a nucleus of 5 to 

7 p; water-clear cells (celhles claires) with no stainable cytoplasm (“one has the 

impression of nuclei floating in an empty space”); dark oxyphil cells (cellules 

sombres) with a longitudinal diameter of 10 p and deeply eosinophilic cytoplasm; 

and pale oxyphil cells (grosses celldes ci prod& gramdegx ozt colloid). 

BOBEAU also examined the parathyroids for fat. He stated that fat was present 

in the cytoplasm of the light chief cells and, more rarely, in the dark oxyphil cells 

but never in the water-clear and pale oxyphil cells. Unfortunately, BOBEAU did 

not give the age of any of his horses, and the correlation between age and the 

degree of fat present in the cells is therefore lacking. 

VERMEULEN (1917) described two main epithelial cell types, viz., chief cells 

and oxyphil cells. He also proposed a classification of the parathyroid glands 

according to the amount and arrangement of connective tissue within the glands. 

Fig. 3. Lower parathyroids of horses, both male and 12 years old. Parathyroid at 

straight arrow, cyst at curved arrows, x 4.5. 

Fig. 4. Horse, female, 22 years old. Relative size of parathyroid glands. Left part 

of figure: upper gland; right part: lower gland, x 5. 

Fig. 5. Horse, female, 17 years old. Typical structure of parathyroid gland. Thin 

connective tissue septa subdividing gland into fine lobuli. Rich vascularization. 

Mainly light chief cells. H & E, x 275. 

Fig. 6. Horse, male, 1 year old. Relatively abundant stroma in parathyroid gland. 

Numerous KURSTEINER’S canals (straight arrow) and cysts (curved arrows) at 

hilus. H & E, x 22.5. 



'I'hc hlicroscopic Anatomy of the Equiiic Parathyroid Glands 11 



12 The Anatomy of the Parathyroid Glands in thc Horsc 

b) Present Investigation 

Metbods. The upper parathyroids were dissected immediately after 

euthanasia (15 horses) or as soon as possible and never later than 

5 hours after death (21 horses). After being weighed, they were split 

and fixed in Bouin’s solution. One-half of each gland was embedded in 

paraffin, sectioned at 4 to 6 p, and stained with hematoxylin and eosin. 

The other half was used for frozen sections at 8 p and stained with 

scarlet red. Serial sectioning was not employed. 

The parenchyma to interstitium ratio and cytoplasm to nucleus 

ratio were determined according to CHALKLEY (1 943). Briefly, 

CHALKLEY’S procedure is as follows : A number of hairs (four, perhaps) 

are attached to the eyepiece diaphragm, the end of each hair representing 

a “point” in the microscopic field. If the cytoplasm to nucleus ratio 

is to be determined, the “hits” of the “points” in the cytoplasm and 

the nucleus, respectively, are recorded in randomly chosen areas. To 

avoid a “purely psychologic but very real difficulty,-a very short 

extra hair is glued on the eyepiece diaphragm; then the focus is so 

made that the tip of this hair is brought into coincidence of the focus of 

a selected object, usually a nucleus. The position of this point is not 

recorded, but the other points alone are used” (CHALKLEY). Twentyfive 

hits in the smaller component of the tissue (the nucleus when the 

cytoplasm to nucleus ratio is calculated) are recorded. At the same 

Chart 2. Parenchyma to interstitiurn ratio in upper parathyroids of 36 normal 

horscs. Ratio on Y-axis, agc in years on X-axis, o = male horses, 1 = female 

horscs. Solid line ~ regression line of ratio as a function of age. 



’The I\licroscopic Anatomy of the Equine Parathyroid Glands 13 

time, let us say, 71 hits in the cytoplasm were recorded. The ratio of 

cytoplasm to nucleus hits is, then, 71 : 25 -= 2.84. According to 

JiiNssoN (1960), who employed this method in his studies on the 

parathyroid function in bovine parturient paresis, six such ratios, 

corresponding to 150 hits in the smaller tissue component, are suffi- 

cient for statistical analyses. 

The nuclear surface was estimated from camera-lucida drawings 

at a magnification of about 1,700 times. Fifty nuclei were so drawn 

from both the left and right upper parathyroid of every horse. The 

nuclear surface was then measured with a planimeter. When conven- 

tional measures are used in the text or tables, they have been extra- 

polated from planimeter units. 

The lower parathyroids were examined only with conventional 

histologic methods. Functional analysis was not undertaken. 

Kt?J//ltJ 

Upper I’aratJydr 

Iizterstitial tiswe. Upper parathyroids were surrounded by a wellcollagenized, 

rather thin fibrous capsule. Thin septa from this capsule 

irregularly crisscrossed the parenchyma, which was thus subdivided 

into fine lobules (Fig. 5). The connective tissue occasionally formed 

large dense areas without epithelial admixture. The amount of interstitial 

tissue varied considerably in different areas in the section 

(Figs. 6 and 7). The variation among horses (Chart 2; for analysis, see 

Appendix, Table 11) was highly significant. On the other hand, there 

were no significant changes in the amount of connective tissue due to 

age (Appendix, Table 11). The upper and lower percentage figures for 

interstitial tissue in 72 equine parathyroids were 50 and 13, respectively. 

The glands were richly vascularized, with the capillaries in close 

contact with lobules (Fig. 5) or epithelial rows. The degree of interstitial 

fat is summarized in Table I. Large fat droplets were present in 

a thin layer just beneath the capsule in about 40 per cent of the glands. 

The fat content did not change with age. In more than 40 per cent of 

the parathyroids the intraglandular connective tissue showed large fat 

droplets, and in rare cases this accumulation of fat cells could be 

impressive (Fig. 7). 

Epithelial tiss//e. Four more or less well-defined cell types were 

observed in the equine parathyroid glands, viz., light chief cells, dark 

chief cells, water-clear cells, and pale oxyphil cells. 



14 ’I’he Anatomy of the Parathyroid Glands in the Horsc 

The ligh chief cells predominated in horses of all ages. The cells 

were arranged in small lobuli, often in a “rosette” configuration 

(Figs. 5 and 8) with a capillary in the center. The cells were almost 

circular in outline, sometimes polyhedric or, more rarely, rectangular. 

The cell margins were variable, sometimes being poorly defined and 

other times standing out well. The cytoplasm was faintly acidophilic 

with hematoxylin and eosin, but the tinctorial properties varied con- 

siderably. With, basic dyes the cytoplasm was diffusely and rather 

faintly blue. Tiny spherical, more deeply basophilic structures, the 

so-called juxtanuclear bodies, were seen occasionally. They were not 

always confined to the immediate vicinity of the nucleus. The nucleus 

was well defined and most often located in the center. However, in the 

above-mentioned rosettes a peripheral location was more common. 

One or two nucleoli were present. The size of the light chief cell and 

its nucleus is given in Table I1 and in Charts 3 and 4 (for analysis, see 

Appendix, Table 11). 

Scarlet red stain revealed fat in the cytoplasm of the light chief 

cells to the degree and frequency shown in Table I. In all positive 

cases but one, small sudanophilic droplets were present in rather small, 

rather well-circumscribed areas of light chief cells. The fat accumula- 

tion was never great enough to give a negative image on the embedded 

section. In one case, that of a male 8-year-old horse, there was a 

diffuse, moderate fatty metamorphosis of practically all light chief cells 

in the section. As may be seen from Table I, parenchymatous fat was 

present mainly in adolescent and young adult horses but was very 

rarely recorded in older horses. 

Dark chief cells were rare. They did occur in horses of all ages, 

however. The size of these cells is given in Table 11. The cell outline 

was poorly defined and the cytoplasm was deep purple. The nucleus 

was elongated, with the length usually double the width. It was deeply 

and homogeneously basophilic and a nucleolus was therefore not 

visible. The dark chief cells contained no fat. 

Water-clear cells occurred at any age, but they were relatively 

rare in the newborn horse in this series. In a few horses less than 1 year 

of age they were quite frequent, although the light chief cells pre- 

dominated. It cannot be said, however, that water-clear cells increased 

with age. In some of the oldest horses they were relatively scarce. 

The water-clear cells were slightly larger than the light chief cells 

(Table 11). In the fully developed stage the cytoplasm showed no 

aHinity with any stain, but the cell outline was much thicker and better 



10 . 

9 . 

a . 

7 0 + 

6 . 

5 . 0 

’I’he ;\licrosc(ipic Anatomy of the Equine I’arathyrciid (;lands 15 

?O 

0 

o + 

+ 

t + 0 + o a 

+ + 8 + 

+ 

4 - +o 0 0 

0 

3 . 

2 . 

1 . 

0 

0..1..2..3..4..5..6..7..~..9.10.11.12.13.14.15.16.17.18.19.20.21.22.23.24 

36 0 

34 0 

32 . + ., 

30 

28 

26 

24 

22 

+ 

+ 

o * 

o * 

0 

0 

0 

0 

+ 

0 

+ 

n 

+ 

+ 

0 

0 

0 0 

Char/ 3. Cytoplasm to nucleus ratio in parathyroid epithelial cells of 36 normal 

horses. Ratio on Y-axis, age in years on X-axis, o ~ malc horses, -1 ~ fctnalc 

horses. Solid line rcgrcssion line of ratio as a function of age. 

Char/ 4. Nuclcar sufacc (in planimeter units) in parathyroid epithelial cells of 

36 normal horses. Surface size on Y-axis, age in years on X-axis, o malc horses, 

I fcmalc horses. Solid line ~ rcgcssion line for nuclear surface size as a 

function of age. 



+ 

+ 

0 

0 

0 

0


7nlile I. Stainable fat 11-1 the upper parathyroid glands 

Sen As, lntcrstitial fat Parcnchy matous 

years Subcapsular Intraglandular fat 

F 4/12 I I I 

F 8/12 l i I ' 

It1 8/12 I I I I 

I; 9/12 I 1 

r 2 I I 

I\ 1 2 I/r 1 I 

At 5 I 

hl 6 I 

IZI 6 

h1 7 

F 8 

hl 8 I 

hl 8 

P 10 I 

A1 11 

F 13 

r 13 

F 14 I 

hl 1s I ' 

21 15 

hl 16 1 

ill 18 I 

ill 24 

17123 10123 9123 

+, slight amount of fat. + +, modcratc amount of fat. + + -I-, abundant amount 

of fat. 

Table II. Sizc of epithelial cclls in upper parathyroid glands 

Nuclcus Nuclcus Cell Cell Cytoplasm/ 

diameter surface diamctcr surface nucleus 

I' sq. /I 1' sq. /( ratio 

Light chief cells 4.9 19 10.8 117 5.3 

(11 ~ 3,600) 

Dark chicf cells 

(I1 = 20) 

4.0* 10 6.5* 30 2.7 

Watcr-clear cclls 4.2 14 11.1 124 7.8 

(I1 ~ 100) 

Pale oxyphil cells 

(11 = 20) 

* 1ong.itudinal axis 

5.1 20 17.0* 220 10 



‘The hl icroscopic Anatomy of the Equinc Parathyroid Glands 17 

7aOlr. IIZ. Iticidcticc of embryologic rudiments associated with thc uppcr parathyroid glands 

Sex Age, Epithelium on 1

18 'I'hc Anatomy of the Parathyroid Glands in the Horse 

defined than that of any other cell (Figs. 8, 9, and 10). In intermediate 

stages the basophilic cytoplasmic structures coalesced to form small 

spherical bodies, crescentshaped flakes, or more irregular formations. 

The spherical bodies could occur at a juxtanuclear position, but when 

they were multiple, as was often the case, they could also occur in the 

extreme peripheiy of the cell. The flakes occurred irregularly in the 

cytoplasm. The more complete the development of the waterclear 

cells was, the more peripheral was their location. The well-defined 

membrane of the water-clear cells was due to the presence of such 

coalesced flakes glued like tapestry to the cell membrane. The cyto- 

plasm contained no stainable fat. The nucleus was smaller than it was 

in the light chief cell and the cytoplasm to nucleus ratio, therefore, 

increased (Table 11). 

Pale oxyphil cells were rare. They were present in horses 10 years 

of age and older. The incidence did not increase with increasing age; 

they were always rare. Usually they occurred singly, but sometimes 

they were in pairs (Fig. 9) or, very rarely, in islands of three or more 

cells. The cytoplasm of these huge cells (Table 11) was slightly granular 

and intensely pink. The nucleus was circular and deeply basophilic, 

and the nucleoli were sharply demarcated. The pale oxyphil cells did 

not contain stainable fat. 

At this point it may be worth while to describe an artifact that 

occurred in a few cases. Fig. 10 shows a well-circumscribed area in 

which the cytoplasm was finely granular and intensely pink. Under 

low or medium-high magnification the cells were at first confused with 

pale oxyphil cells. Under oil immersion (Fig. 10, insert) it could be 

seen, however, that the cell borders were disrupted and that the well- 

/;(

’I’hc hlicroscopic Anatomy of thc Equine I’arathyroid (;lands 19 



20 ‘The Anatomy of the Parathyroid Glands in the Horse 

preserved nuclei were, instead, surrounded by hemolyzed or shrunken 

erythrocytes. These artifacts always occurred just beneath the capsule 

and never deep in the gland. It may be reasonable to assume that these 

hemorrhages occurred when the parathyroids were dissected from a 

horse just sacrificed and that the fixative (BOUIN) caused the hemolysis 

and shrinkage of the erythrocytes. 

Embvologic r/idiments. The incidence of embryologic rudiments 

associated with the parathyroid glands is given in Table 111. 

Epithelial remnants of the thymus-parathyroid communicating 

segment occurred on the external surface of the parathyroid capsule in 

a few cases. It was found in immediate relation to the parathyroid 

hilus, i.e., the posterior ventromedial aspect of the gland where the 

vessels enter and leave the gland. The epithelium was usually seen as a 

direct continuation of a huge cyst invaginated into the hilus. Ciliated 

high (Fig. 11) or flattened elongated cells spread out on the external 

surface of the parathyroid capsule, which they embraced for a relatively 

short distance, and then they gradually disappeared. 

KURSTEINER’S canals or cysts (Figs. 12 and 13) were found at the 

hilus in a very large number (92%) of the glands (61) in which the 

section included the hilus. No attempt was made to classify these 

rudiments according to GILMOKJR’S (1937) types. All three types 

occurred. Glandlike structures, fulfilling the criteria of GILMOUR’S 

type 2, could suddenly become cystic and match the description of 

type 3. Almost every type of lining epithelium was observed: ciliated 

cylindric, cuboidal, stratified, and elongated flat. A strongly basophilic, 

structureless material with an admixture of desquamated epithelium 

and blood cells was present in most cysts. A few cysts were 

empty; the rudimentary canaliculi were usually so. The size of the 

Fig. 11. Horse, male, 11 years old. Ciliatcd epithelium (arrows) on cxtcrnal surface 

of parathyroid capsulc. Light chief cells inside fibrous capsulc. H & E, oil immcr- 

sion, x 720. 

F

‘I’lic ihlrcroscopic Anatomy of thc Eqiitnc I’arathyrotd Glands 21 



22 The Anatomy of the I'arathyroid Glands in the Horse 

F'&. 15. Horse, female, 10 months old. Large thymic rudiment included within 

parathyroid capsule. 'Thymus cortex and mcdulla with I-Iassall's body. Parathyroid 

tissue madc up by lisht chief cells. Subcapsular fat present. EI Kc E, x 180. 

Fi,.. 16. Horse, male, 6 ycars old. Thymus (upper part), thyroid (middlc part), and 

parathyroid (lowcr part) mixcd up without distinct dcmarcation. 1-1 Kc E, x 100. 

embryonic rudiments varied within a wide range. Canaliculi with flat 

epithelium were rather small, even when they were subject to cystic 

dilatation. The cysts varied from 10 to 15 p up to 2 cm. in diameter. 

Cysts and occasional canaliculi were less frequent within the 

parathyroid glands than in the connective tissue at the hilus. Still they 

were present in 46% of all parathyroid glands. The size varied from 

microscopic to 1 cm. in diameter. Solitary and multiple (Fig. 14) cysts 

occurred. The lining epithelium and the cyst content showed the same 

variations as did corresponding structures at the parathyroid hilus. 

Thymus rudiments were found in over 26% of the parathyroid 

glands. They occurred at the hilus inside the parathyroid capsule or, 

more rarely, deep in the gland irregularly mixed with parathyroid 

tissue. In some cases only tiny islands were present, but in others 



‘I’hc Alicroscopic Anatomy of the Equine Parathyroid Glands 23 

7’~tbli. I I -. Incidciicc of cmhryologic rudimcnts associated with the loa.cr parathyroid glaiids 

sex Age, 

years 

1; 2 

I? 10 

A1 12 

hi 12 

I\ 1 12 

1: 19 

1: 20 

I: 22 

~ 

Epithelium on I

24 ’l’hc Anatomy of the Parathyroid Glands in thc Florsc 

I,ower Parathyroids 

The architecture, cell types, etc., of the lower parathyroids were 

identical to those described for the upper parathyroids. The incidence 

of embryologic rudiments in the lower glands is given in Table IV 

(see also Fig. 3). 

4. Discussion 

The existence of two pairs of parathyroid glands in the horse was 

demonstrated by Hi\smmno and 1L4ro (1932) and the present study 

is in agreement with their findings. The nomenclature will now be 

discussed. 

Previous to I-IASHIMOT’O and KATO (1 932) the discussion on “external” 

and “internal” parathyroids concerned the relationship to the 

thyroid gland. After HAsHImmo and I

Discussion 25 

7bbic 1 .. Avcragc size atid rclativc weight of equine parathyroids 

Source 1,cngth Width Height Relative weight 

mm. mm. mtn. mg./kg./bodyweigh 

H4bii1~0.m and J

26 ‘I’hc Anatomy of the Parathyroid Glands in the 1 lorsc 

7Uble I 7. Relative weight or vulumc of the parathyroids of sr)mc mamtnals 

Alan (DANISCII, 1924) 

]\IONKEY, fcmalc (BAIXR, 1942) 

~IONRI:Y, malc (BAKI;IT, 1950) 

Rat, malc, 65 days (,Id (F,NT, 1950) 

Rat, malc, 80- 90 days old (Er\lc;i,i:r.u.r, 1950) 

Rat, malc, 150-200 days old (ENT, 1950) 

1,s - 2.0 11 ig 

1.4 iiiin:1 

1.1 inin:] 

1.32 mg. 

1.70 mm:{ 

1.12 mm:< 

0.89 mm:{ 

0.67 inin:$ 

pcr kg. of body \\.eight 

per Icg. of body \\.eight 

per kg. of body \\.eight 

per kg. of hotly weight 

pcr kg. of body Ivcight 

pcr kg. of lx)dy \vcight 

per kg. of I J O ~ \\,eight 

~ 

per kg. of body \\.eight 

The discrepancy between the two series is believed to be due to 

the fact that nutritional secondary hyperparathyroidism is extremely 

frequent in Japan (see Chapter 11). The material of f1asrrr~io~i~o and 

KATO very likely included subclinical cases of hvperparathyroidism. 

MI~ISSNI~R (1958) and GKAU and DIJLLMANN (1958) erroneously 

quoted HI\si-IIwnu and I

Discussion 27 

Table VZZ. Nuclear size and cytoplasm/nucleus ratio of parathyroid cells in man 

and horse 

Ma,, Horse 

Nuclear size C/N Nuclear size C/N 

planimeter ratio sq. ,LL ratio 

units 

Dark chief cells 9.9-1 3.5 1.69 10-12 2.5 

Light chief cells 13.7-1 7.3 2.44 18.66 5.28 

Small water-clear cells 12.7-1 7.1 2.88 - 

Large water-clear cells 16.3-21.9 5.76 14.02 7.81 

Dark oxyphil cells 11.2-18.0 4.05 - 

Pale oxyphil cells 9.2-14.6 8.56 19.71 10 

It should be noted that EGER and VAN LESSEN gave the size of the 

nuclei in planimeter units. Their figures are therefore not directly 

comparable with those for the horse, which are given in conventional 

measures. 

Because of the changing nuclear size and the cytoplasm to 

nucleus ratio in the different cells, EGER and VAN LESSEN (1954) felt 

that the functional capacity increased from the resting dark chief cell 

through the small water-clear cell and then gradually decreased to no 

activity in the pale oxyphil cell. TRIER (1958), however, showed in 

electron micrographs, that the typical granulation of the oxyphil cells 

was due to accumulations of mitochondria. He thus established that 

the oxyphil cells are highly active metabolically. He was confirmed in 

1961 by independent investigations by BALOGH and COI-IEN and by 

TREMBLAY and CARTIER which showed that the highest enzymatic 

activity was present in the oxyphil cells. 

Although the size of the cytoplasm and, consequently, the cytoplasm 

to nucleus ratio of all parathyroid cells are considerably greater 

in the horse than in man, the tinctorial properties of these cells 

justifj the use of the same nomenclature in the two species. 

It is difficult to make an evaluation of the parathyroid activity as a 

function of individual horses, sex, and age from our material. With the 

great variations in the parenchyma to interstitiurn ratio and with the 

high incidence of embryologic rudiments in the parathyroids, weight 

as such is of little or no importance in the evaluation of the functional 

state. The regression line of the relative weight of the upper parathyroids 

as a function of age showed a slight but insignificant decrease. 

There were no differences between the sexes, but the variation between 

horses was remarkable. The parenchyma to interstitium ratio, the 

3 Krook/Lowe 




cytoplasm to nucleus ratio, and the nuclear size of the epithelial cells 

increased with age, but this was not significant. These values were also 

independent of sex, but they varied significantly between horses. The 

material does not therefore indicate any changes in parathyroid 

function in the horse due to sex or age. 

Parenchymal fat was present in the equine parathyroid glands of 

horses aged 4 months or more. The majority of horses up to 8 years of 

age showed a little fat in restricted areas of light chief cells. Only 1 of 

11 horses 10 to 24 years of age had parenchymal fat. This is exactly 

opposite to the condition in man and the dog. In a review article 

BARGMANN (1939) stated that parenchymal fat makes its appearance in 

the human parathyroid at the latest during the 20th year of life (in rare 

cases as earIy as the fourth month) and that the fat content then 

increases continuously. In the dog parenchymal fat in the parathyroids 

starts to appear at the age of 3 years and, as in man, increases with 

increasing age. The presence of stainable fat in epithelial cells of the 

parathyroids is variously interpreted. BOBEAU (1 91 1) hypothesized that 

this fat represented degenerated and conglomerated mitochondria (fat 

phanerosis in Virchow’s sense) whereas WEIL [(1921), quoted from 

BARGMANN (1 93591 believed that the fat-positive granules in the epithelial 

cells were hormone precursors. These theories have not been 

substantiated. The fat content of the parathyroid cells is not related to 

the nutritional condition of the individual [BARGMANN (1 939)]. 



11. Nutritional Secondary Hyperparathyroidism in the Horse : 

Review of the Literature 

1. The Nature of the Osteopathy 

Metabolic bone diseases characterized by “too little mineralized 

bone” can occur, pathogenetically, for three reasons [ALBRIGHT and 

REIFENSTEIN (1948)] : 

A. Bone formation too little 

a) Defect in matrix formation: Osteoporosis. 

b) Defect in mineralization of matrix: Rickets in young individuals, 

osteomalacia in adults. 

B. Bone resorption too much 

a) Generalized osteitis fibrosa. 

Bone as a tissue [in the sense of WEINMANN and SICHER (1955)] is 

formed in only one way, that is, by apposition of osteoid by osteoblasts. 

POMMER (1885) defined osteoporosis as an osteoblastic deficiency. 

Osteoporosis is, accordingly, a metabolic bone disease due to 

too little matrix formation. The catabolic processes are not influenced, 

and the net result over a long period of time is loss of bone. Although 

POMMER’S view has been violently debated, nothing has appeared to 

disprove him. Etiologically, however, the nature of osteoporosis 

remains obscure in most cases [MCLEAN and URIST (1961)]. 

In rickets and its adult counterpart, osteomalacia, “too little 

mineralized bone” results from too low ion product of calcium and 

phosphorus in the blood serum [IVERSEN and LENSTRUP (1919)l. This 

lowered ion concentration may be due to a decrease in serum calcium 

or phosphorus or both. With regard to the pathogenesis we recognize 

a low-calcium rickets and a low-phosphorus rickets. The causes for 

lowered serum calcium and/or phosphorus are numerous. They have 

been reviewed by FOLLIS (1958). 

Generalized osteitis fibrosa as a separate entity was described in 

1891 by VON RECKLINGHAUSEN. The cause of this generalized bone 



30 Nutritional Secondary Hyperparathyroidism in the Horse 

disease is hyperparathyroidism, of which there are two main types, 

primary and secondary. The primary form, caused by parathyroid 

neoplasia or primary hyperplasia, serves no purpose at all. The resulting 

generalized osteitis fibrosa is only the regrettable result of an 

uncontrolledexcessiveparathormone incretion. The primary role of the 

parathyroid(s) in VON RECKLINGHAUSEN’S disease was established in 

1925 with MANDL’S surgical removal of a parathyroid adenoma which 

resulted in the healing of generalized osteitis fibrosa in a man. Secondary 

hyperparathyroidism, on the other hand, is of a compensatory 

nature. It is caused by hypocalcemia [HAM et al. (1940); PATT and 

LUCKHARDT (1942); STOERK and CARNES (1945); ENGFELDT et al. 

(1954); among others], and its purpose is to correct this hypocalcemia. 

The hypocalcemia may be secondary to hyperphosphatemia due to 

chronic renal insufficiency. Parathyroid hyperplasia of this origin was 

first described by BERGSTRAND in 1921. In this renal secondary hyperparathyroidism 

the bone lesions may predominate, especially in young 

individuals, and misleading terms such as renal rickets, renal dwarfism, 

and “rubber jaw disease” have therefore been introduced. 

Hypocalcemia can further result from low calcium feeding or, 

secondarily, from excessive phosphorus feeding. In both instances 

parathyroid hyperplasia will occur. If hypocalcemia results from low 

calcium feeding with normal (or low) phosphorus intake, rickets and 

generalized osteitis fibrosa may occur simultaneously [MAREK and 

WELLMAN (1 931)]. If, on the other hand, the hypocalcemia is secondary 

to excessive phosphorus intake, the ion product of calcium and phosphorus 

in the blood serum exceeds the normal. In this case the hyperparathyroidism 

is not accompanied by rickets. Nutritional secondary 

hyperparathyroidism is not known to cause generalized resorption of 

bone in man [BERGSTRAND (1956)l. In domesticated animals such a 

nutritional secondary hyperparathyroidism with generalized osteitis 

fibrosa, sometimes very severe, is of fairly common occurrence. It has 

been described in the horse, cow, goat, monkey, pig, dog, and cat. 

Our concepts of the metabolic bone diseases of the “too little 

mineralized bone” type are based on relatively recent research. It is 

therefore not surprising that the nomenclature applied to what should 

be called “nutritional secondary hyperparathyroidism” has been 

variable. 

The disease of horses under consideration has been known since 

ancient times. Probably it was this disease that was described as 

“animal osteomalacia” by VEGETIUS about 400 A. D. The first reliable 



The Nature of the Osteopathy 31 

Fig. 17. HAUBNER’S illustration of “osteoporosis of a peculiar nature.” Reproduced 

from .!Wag. ges. Thierhcilk., 1854. 

description appears to be that by RYCHNER in 1851. His case was a 

2-year-old horse that had developed a slow, troubled chewing which 

was not related to the second dentition or a tooth disorder. Both 

maxillae showed a uniform swelling that extended backward to the 

level of the last molars. The entire mandible evidenced a moderate, 

diffuse swelling. The hyperostotic bones were somewhat warmer than 

normal and yielded to pressure. The swelling progressed rapidly, and 

the hollow percussion sound over the nasal and maxillary sinuses 

disappeared. The horse was destroyed. On post-mortem examination 

the skull bones were easily breakable, the cut surface showed multiple 

cysts filled with a semigelatinous, somewhat hemorrhagic fluid, and 

the teeth were freely movable in their alveoli. After maceration the 




right mandibular ramus appeared like pumice stone. There can be 

little doubt that the lesions of the skull bones were those of osteitis 

ilbrosa cystica. RYCHNER did not commit himself to a diagnosis. The 

disease exhibited, he stated, some similarities to osteomalacia and some 

to osteoporosis. 

HAUBNER (1854) gave a most detailed account of the condition in 

an 8-year-old riding horse, which had been developing the symptoms 

for 2 years. His description of the necropsy emphasized the generalized 

nature of the skeletal changes: “All bones, without exception, show 

signs of the disease. The lesions are most pronounced in the flat 

(Fig. 17) and so-called mixed bones and are less striking in the long 

bones.” The following is quoted from his histologic description : 

“The microscopic examination of thin slices of different bones always 

reveals one change in the bone. This change is that the Haversian canals of the 

compact bone are considerably larger than normal. On longitudinal section it is 

observed that the widcning of these canals is not uniform; in some areas the canals 

arc two or three times as wide as in others.” 

In the same communication HAUBNER described the disease in a 

pig. His histologic observations are remarkable : 

“With the help of my colleague PISCIIEL it was proved that an osteoporosis 

was present here also. It was concluded, however, that the osteoporosis was of a 

peculiar nature, hitherto never described in textbooks on pathologic anatomy. It 

differed as I have already pointed out, from the medullary porosis, which it otherwise 

resembled very closely, mainly in the respect that a firm fibrous cellular 

tissue occupied the bone space and, which I like to add, contributed to the enlargement 

of the bones, although it may not have been the only cause of this enlargement.” 

This is a clear-cut description of generalized osteitis fibrosa. It 

was given in 1854, 4 years before VIRCHOW’S Cellzdar Pathology 

appeared, 19 years before KOLLIKER published his classical treatise on 

resorption of bone, and it anticipated VON RECKLINGHAUSEN’S description 

of generalized osteitis f-ibrosa in man by 37 years. 

In agreement with HAUBNER, DOR (1902) showed that the osteopathy 

in maladie dzt son is generalized; he applied the term “rarefying 

osteitis”. He believed that the horse disease was comparable to 

PAGET’S (1877) osteitis deformans but noted a difference between the 

two conditions. In PAGET’S disease the cranial bones are more commonly 

involved than the jaws, which DOR, like earlier and later investigators, 

found to be most severely affected in the horse. 



’The Nature of the Osteopathy 33 

The term “osteitis fibrosa” for the osseous lesions in nutritional 

secondary hyperparathyroidism in the horse was first used by JOST 

(1910). He gave a detailed description of the histologic changes in the 

skull bones of a 6-year-old horse. He described all anatomical characteristics 

of osteitis fibrosa and presented several photomicrographs to 

support his diagnosis. JOEST and ZUMPE (1924) showed that other 

bones (cervical vertebra, humerus, femur) exhibit the same changes. 

The investigations by JOST and by JOEST and ZUMPE 

thus revealed that 

the osteopathy in bran disease is a generalized osteitis fibrosa. Nevertheless, 

the later literature does not show any uniformity in nomenclature. 

The disease continued and continues to be described as 


Table WII. Dietary calcium and calcium to phosphorus ratio in experimental 

nutritional secondary hyperparathyroidism in the horse 

G. Ca/day Ca : P Occurrence of symptoms 

ratio 

STURGESS and CRAWFORD (1927) 20.1 1 : 3.1 After more than 9 months 

NIIMI (1927) 1.5 1 : 8.1 After 5 months 

NIIMI and AOKI (1927) 2.6 1 : 8.1 After 5 months 

GROENEWALD (1937) 3.4 1 : 7.0 After 9 months 

Table ZX. Normal calcium and phosphorus requirement in the horse 

Growing horses (360 kg. mature weight) 

8 months old 

19 months old 

44 months old 

Growing horses (540 kg. mature weight) 

6 months old 

14 months old 

44 months old 

G. &/day Ca : P 

ratio 

17 1.3 : 1 

13 1 :1 

9 1 : 1 

15 1.3 : 1 

14 1.2 : 1 

11 1 :1 

the exception of 22 severely affected animals, all showed improvement 

within 3 weeks. LANE corrected two other outbreaks in the same 

manner. 

INGLE (1909) developed a theory to explain the etiology based on 

LANE’S study of the disease in South Africa. INGLE was interested in 

the mineral constituents of horses’ diets, primarily calcium oxide and 

phosphorus pentoxide. He pointed out that oat hay and Indian corn, 

the basal diet for many South African horses and mules, resulted in a 

large excess of phosphorus over calcium. He noted that, although no 

experiments using diets with high phosphorus in proportion to 

calcium had been reported in horses, WEISKE (1891) had experimented 

with such diets in rabbits. Avery light-weight, fragile skeleton resulted. 

Calcium carbonate added to the diet prevented the fragile bones. INGLE 

then reviewed LANE’S method for treating the disease and concluded 

that the results occurred because LANE supplemented the diet with 

more calcium than phosphorus. INGLE thus concluded that a calcium 

source alone was needed to treat or prevent nutritional secondary 

hyperparathyroidism. 



Etiology 35 

Experiments and clinical studies since INGLE’S report have 

supported him fully. The optimum calcium to phosphorus ratio in the 

feed is now considered to be 1 : 1 [Natl. Acad. Sci. (1961)l. KINTNER 

and HOLT (1932) in feeding trials using affected horses found that 

excessive bone resorption was arrested when the ratio was 1.17 : 1 or 

above and that excessive resorption progressed when the ratio was 

decreased to 1 : 1.41 or below. 

The absolute amounts of calcium and ratios used in the experimental 

reproduction of the disease are summarized in Table VIII. 

In above reports as well as in that by KINTNER and HOLT, the 

ratios of calcium oxide and phosphorus pentoxide were given. The 

values given in the above list refer to calcium and phosphorus, instead. 

The normal requirement for the horse [Natl. Acad. Sci. (1961)l is 

given in Table IX. 

3. Occurrence and Breed, Sex, and Age Predsposition 

Nutritional secondary hyperparathyroidism in the horse has been 

described, under varying terms, from countries all over the world 

according to the review by KINTNER and HOLT (1932). Mbcs~ (1959), 

however, referred to the disease as an “extra-European’’ osteodystrophy, 

which is surprising because the disease was first described in 

Switzerland [RYCHNER (1851)l and because the nature of the bone 

lesions was first revealed, as we have seen, in Germany [JOST (1910)l. 

The incidence varies considerable. Sporadic cases as well as 

“enzootic” outbreaks have been reported. STURGESS and CRAWFORD 

(1927) stated that at least 10% of all horses in Ceylon were affected to 

some degree. KINTNER and HOLT (1932) reported that about 15% of 

the U. S. Army horses on native feed in the Philippines were affected in 

1930-1931. In the first six months of 1931 no less than 285 cases were 

diagnosed. The disease accounted for more than one-fourth of all 

hospitalized horses. YAMAGIWA and SATOH (1956) reported 499 cases 

from 1951 to 1956 at their pathology department in Japan, which 

certainly indicates a very high incidence. 

No breed predisposition has been reported, and sex is not a 

predisposing factor either. In accordance with the fact that the calcium 

requirement is higher during pregnancy [Natl. Acad. Sci. (1961)], 

KINTNER and HOLT (1932) showed that all investigators had agreed 

“that pregnancy may influence the development and/or the course of 




the disease”. Young growing animals develop the lesions faster and 

more severely than older ones. Increasing age does not, however, 

produce resistance. 

4. Symptoms 

The first symptom is usually an insidious, shifting lameness 

[VARNELL (1 860), and most subsequent investigators]. A general 

tenderness of the joints and a stiff, stilted gait then occur. Muscular 

weakness, trembling, and a tottering motion when in motion have 

been described. Some animals prefer to canter rather than to trot; 

others refuse to move and if forced to do so inch along in a most 

crippled fashion. Spontaneous fractures and spontaneous avulsion of 

ligaments have been noted in all extensive outbreaks. 

Although lameness is the first sign, the most severe changes 

occur in the skull bones, notably the jaws. The maxilla and, usually to 

a lesser degree, the mandible and nasal bone may later exhibit a hyperostotic 

osteitis fibrosa. This swelling hasgiven the disease the expressive 

name “bighead” [LANE (1906); STURGESS and CRAWFORD (1927) ; 

KINTNER andHoLT (1932); OLIVER (1933); THEILER (1934); GREENLEE 

(1939); and others]. 

The appetite is normal; pica may occur [HAUBNER (1854)l. Due to 

extensive resorption of bone around the teeth mastication problems 

usually occur late in the course of the disease. This may, however, be 

the first sign [RYCHNER (185l)l. 

The duration varies and is apparently related to the degree of 

calcium to phosphorus imbalance in the feed. HAUBNER (1 854) observed 

a case for over 2 years; VARNELL (1860) gave a time of 6 months. The 

disease is not fatal in itself, but animals may die form starvation due to 

impaired mastication. More commonly, however, the horses are 

destroyed because of locomotor disturbances, especially when 

fractures occur. 

5. Clinical Pathology 

NIIMI and AOKI (1927) reported decreased blood serum calcium 

levels in their two experimental cases of nutritional secondary hyper- 

parathyroidism in mature horses. The average level was 13% lower 

than in two controls. Blood serum phosphorus was elevated 23% at 

the same time. Blood determinations were made only once. 



Clinical Pathology 37 

Table X. Serum calcium and phosphorus in spontaneous nutritional secondary 

hyperparathyroidism in the horse (KINTNER 

and HOLT) 

Calcium Phosphorus 

mg./100 ml. mg./100ml. 

Normal horses, n = 96 

Maximum 14.3 5.00 

Minimum 10.2 2.63 

Average 11.2 3.55 

Horses with nutritional 

secondary hyperparathyroidism, n = 36 

Maximum 12.7 5.87 

Minimum 8.1 3.20 

Average 10.2 4.26 

Samples were taken only once. 

KINTNER and HOLT (1932) studied a wide range of blood constituents 

in affected and normal horses. Differences existed only with 

regard to calcium and phosphorus (Table X). 

GROENEWALD (1937) reported that blood serum calcium, phosphorus, 

and alkaline phosphatase were normal inhis three experimental 

cases compared to two controls. 

No reports of a series of determinations of serum calcium, 

phosphorus, and alkaline phosphatase made during the experimentally 

induced course of nutritional secondary hyperparathyroidism in the 

horse have been found in available literature. 

6. Roentgenologic Changes 

KINTNER and HOLT (1932) used radiographs as an aid to diagnosis. 

Anteroposterior views of the metacarpi were taken. The progress was 

followed radiographically with follow-up plates taken 3 months after 

the initial ones. Correlation with clinical symptoms was good. Cortical 

and medullary portions blended together to give a hazy, irregular 

appearance to the line of separation. The medulla was widened at the 

expense of the cortex. Longitudinal striations of decreased density 

were apparent in the cortex in varying degrees. 

GROENEWALD (1937) also radiographed the metacarpi of his 

experimental horses. He did this once, 2 months prior to the time 

severe clinical symptoms were noted. His findings were similar to those 

of KINTNER and HOLT. 




7. The Parathyroid Glands 

KINTNER and HOLT (1932) examined grossly the parathyroid 

glands from horses with “bighead”. They did not list the number of 

necropsies performed but they concluded, “In the present investigation, 

no gross abnormalities have been noted in the glands having 

internal secretions. ” 

THEILER (1934) did not exclude the possibility of endocrine 

changes associated with the disease in horses. “The part possibly 

played by disturbances in endocrine functions, with or without concomitant 

dietary defects, and the possible significance of differences in 

endocrine mechanisms controlling mineral metabolism, are as pet 

unexplored in the domesticated economical animals.” 

HORTA and SANTOS (1944) studied the parathyroid glands from 

three cases of generalized osteitis fibrosa in Portuguese army horses. 

Size and weight of the parathyroids are given in Table XI. 

Body weights were not given; neither is it clear whether the 

weights of the normal parathyroids refer to one or both parathyroids. 

YAMAGIWA et al. (1958) studied the parathyroids from 100 cases of 

generalized osteitis fibrosa. Relative weights were not given, but the 

graphs indicated that the long axis was 19 mm. or more in 75 % of the 

cases. The histologic description was inconclusive, and these workers 

expressed their views on the relationship between the parathyroid 

glands and the osteopathy as follows : “In giving solution to the pathogenesis 

of osteodystrophia fibrosa, the authors would like to hold an 

attitude not to give preceding role to changes of parathyroid glands.” 

Table XI. Size and weight of parathyroid glands in spontaneous nutritional 

secondary hyperparathyroidism in the horse (HORTA 

and SANTOS) 

Generalized osteitis fibrosa Control 

1. Left 12x 12 mm. 400 mg. 

Right 7x 6 mm. 375 mg. 

2. Left - 400 mg. 

Right - 330 mg. 

3. Left - 320 mg. 

Right - 350 mg. 



200 mg. 

50 mg. 

130 mg.

111. Experimental Nutritional Secondary Hyperparathyroidism 

in the Horse: Design of the Experiment 

1. Experimental Animals 

A descriptive listing of the horses is presented in Table XII. The 

three experimental horses will henceforth be referred to as NSH 1, 

NSH 2, and NSH 3 (NSH for Nutritional Secondary Hyperpara- 

thyroidism). 

The colts were purchased in September, 1961, and stabled in two 

adjacent box stalls for 2 weeks prior to the experiment. At ths time 

they were placed in individual cement-floored box stalls. Wood 

shavings were used for bedding throughout the experiment. The 

animals were allowed to exercise at will for 2 to 4 hours daily on 

cement surface in a small paddock. Weather interferred with the 

exercise period during midwinter. 

Parasitologic examination of the feces at the time of purchase 

revealed Strongyle spp. and Parascaris eqttorum ova in a moderate 

number. Following treatment with a piperazine carbon disulfide com- 

plex, fecal examinations at 3-month intervals showed only occasional 

ova and treatment was not repeated. 

Table XII. The colts at the beginning of the experiment 

Number Sex Age Color Condition Body weight 

NSH 1 Male 9 months Dun Fair 195 kg. 

NSH 2 Male 5 months Chestnut Good 205 kg. 

NSH 3 Female 7 months Palomino Fair 148 kg. 

Control Male 8 months White Fair 181 kg. 



40 Experimental Nutritional Secondary Hyperparathyroidism in the Horse. . . 

Table XIII. Experimental Diet 

Nutrient Hay Soft Water Phosphorus Total Standard* 

3.64 kg. wheat 16 L. supplemen- requirement 

bran tation 

2.73 kg. 11.58 g. 

Total 

protein, kg. 

Digestible 

0.26 0.38 - - 0.64 0.50 

protein, kg.** 

Total digestible 

0.19 0.27 - - 0.46 0.34 

nutrients, kg.*** 1.79 1.83 - - 3.62 2.82 

Fat, kg. 0.07 0.11 - - 0.18 not given 

Fiber, kg. 1.09 0.27 - - 1.36 not given 

Vitamin A 56.0 12.0 - - 68.0 3.3 

I.U. x 103*** 

Vitamin D 

I.U.X 103*** 5.7 - - - 5.7 1.2 

Calcium, g. 12.40 2.94 0.46 - 15.80 15.0 

Phosphorus, g. 7.28 39.48 - 11.58 58.14 12.0 

* Standard requirement according to Natl. Acad. Sci. (1961). 

** Digestible protein calculated on assumed 70 per cent digestibility. 

*** Total digestible nutrients, fiber, and vitamin contents calculated according 

to MORRISON (1956). 

Table XIL‘. Control Diet 

Nutrient Hay “Omolene” Water Total Standard 

3.64 kg. 1.82 kg. 16 L. requirement 

Total protein, kg. 

Digestible 

0.26 0.20 - 0.46 5.50 

protein, kg. 0.19 0.14 - 0.33 0.34 

Total digestible 

nutrients, kg. 1.79 1.27 - 3.06 2.82 

Fat, kg. 0.07 0.04 - 0.11 not given 

Fiber, kg. 1.09 0.16 - 1.26 not given 

Vitamin A 

I.U.X 103 56.0 - - 56.0 3.3 

Vitamin D 

I.U.X 103 5.7 - - 5.7 1.2 

Calcium, g. 12.40 8.40 0.46 21.26 15.0 

Phosphorus, g. 7.28 7.80 - 15.08 12.0 

“Omolene”, a grain product of Ralston Purina Company, St. Louis, Mis- 

souri, contains rolled barley, crimped oats, cracked corn, linseed meal, cane 

molasses, wheat bran, alfalfa meal, sodium propionate, 1 yo calcium carbonate 

0.5 yo iodized cobalt carbonate, and zinc oxide. 

Calculations are the same as in Table XIII. 



Ration 41 

Table XI/. Calcium and phosphorus contents of experimental and control diets 

NSH horses Control horse 

Week G. Ca/day G. P/day Ca : P G. Ca/day G. P/day Ca : P 

0-23 15.80 58.14 1 : 3.68 21.26 15.08 1.41 : 1 

24-41 14.17 87.77 1 : 6.19 21.26 15.08 1.41 : 1 

2. Ration 

The experimental and control &ets are given in Tables XI11 and 

XIV. Table XI11 relates to the first 23 weeks. From week 24 through 

week 41 the hay was decreased from 3.64 kg. a day to 2.73 kg. a day, 

the wheat bran was increased from 2.73 kg. a day to 4.09 kg. a day, and 

and the phosphorus supplementation was increased from 11.58 g. a day 

to 23.16 g. a day. The calcium and phosphorus contents during the 

experiment are summarized in Table XV. 

Hy. Timothy hay with minor amounts of weeds and native 

grasses was used. The hay was grown locally and field-cured 2 months 

prior to the beginning of the experiment. Total protein, calcium, and 

phosphorus were determined once from representative samples of 20 

bales of hay. 

Soft wheat bran and “Omolene” (Table XIV) were the grain pro- 

ducts used in the ration for experimental and control horses, respec- 

tively. Total protein, calcium, and phosphorus were determined once 

from 18 bags of bran and 10 bags of “Omoleney’. 

Water. The source of drinking water was the water supply of the 

city of Ithaca, New York. The calcium content was checked twice. 

Phosphoruf supplementation. Monosodium phosphate was given as a 

supplemental phosphorus source to NSH 1, and the other NSH horses 

were given disodium phosphate. The sodium phosphate was of a 

technical grade. The supplement was dissolved in the drinking water 

daily. 

Sodium chloride was fed free choice from blocks in the stalls. 

3. Physical Examination 

The animals were observed daily, and routine physical examina- 

tions were made at monthly intervals. 




4. Clinico-pathologic Determinations 

A 50-cc. sample of blood was taken from either jugular vein prior 

to the afternoon feeding 1 day a week. Calcium, phosphorus, and 

alkaline phosphatase levels in the serum were measured. The calcium 

level was determined according to the method of KRAMER and TISDALL 

(1921) as modified by CLARK and COLLIP (1925); the phosphorus 

according to FISKE and SUBBAROW (1925), and the phosphatase by the 

method of BESSEY et al. (1946). 

5. Roentgenologic Examination 

Intravitul examinations. Radiographs were takenat2-week intervals. 

To control motion the animals were tranquilized (by 200 mg. of 

promazine HC1 intravenously) and placed on an operating table in 

right lateral recumbency. A lateral view of the face was taken, including 

all tissues rostral to the fourth premolar. A lateral view of the 

metatarsus was also taken. A lack of uniformity in the technique and 

an excessive amount of tissue made lateral views of the face difficult to 

interpret. At week 26 and every 2 weeks thereafter a ventrodorsal 

view of the mandible was taken by placing a nonscreen film envelope 

in the animal's mouth. Because of a minimum of soft tissue and no 

superimposition of bones, these views of the rostral end of the 

mandible were superior to views of the entire face. 

Roentgenographic examination of post-mortem specimens. At necropsy 

the soft tissue was removed from the bones and radographs were 

made prior to fixation for sectioning. The radiographs were as follows : 

a) Lateral view of a median longitudinal section, approximately 

1 cm. thick, from all bones of both right limbs; 

b) Proximodistal view of a transverse section, approximately 

1 cm. thick, from the proximal, middle, and distal part of the diaphysis 

of all bones of both left limbs; 

c) Lateral view of each half of the head split midsagitally; 

d) Anteroposterior view of a transverse section of the maxilla, 

approximately 1 cm. thick, at the level of the second molar; 

e) Ventrodorsal view of the rostral third of the mandible; 

f) Lateral view of each half of the mandible split through the 

symphysis ; 

g) Anteroposterior and lateral views of right ribs 3 and 10. 



Necrops y 43 

6. Necropsy 

The animals were destroyed after 41 weeks (NSH horses) and 

42 weeks (control horse) by means of exsanguination under chloroform 

anesthesia. The upper parathyroids were dissected immediately 

after death and weighed to the nearest 0.1 mg. The brain, spinal cord, 

and peripheral nerves were fixed in 10% neutral formalin; other soft 

tissues were fixed in Bouin’s solution. Bone slices approximately2 mm. 

thick were fixed in 10% neutral formalin for 24 hours and then 

demineralized in 10% formic acid to effect. Eleven different areas of 

the skull bones and some 50 different longitudinal and transverse 

sections of other bones were considered representative of the skeleton. 

Paraffin embedding and sectioning at 6 p were employed. Soft tissues 

were stained with hematoxylin and eosin. The parathyroids were also 

stained with scarlet red on frozen sections at 8 p. Bones were stained 

with hematoxylin and eosin and van Gieson’s picrofuchsin hematoxyh. 

The methods used to evaluate the parathyroid function morphologically 

were given in Chapter I. 

4 KrookILowc 



IV. Experimental Nutritional Secondary Hyperparathyroidism 

in the Horse: Results 

1. Clinical Observations 

A. Weight Gains 

All four colts made normal weight gains during the 41 weeks of 

the experiment (Table XVI). Horse NSH 3 was thin at the start but 

made up for this by gaining faster than the other three colts. The 

control animal was on a borderline nutritional level as judged by 

recommended levels (Table XIV). His comparatively low weight 

gains are evidence of this. He refused to eat more than 3.64 kg. of hay 

and 1.82 kg. of grain per day. 

Expected growth for horses with mature weight of 364 kg. is 

0.32 kg. a day [Natl. Acad. Sci. (1961)l. 

B. Clinical Symptoms 

During week 0 through week I2 nothing abnormal was noted in the NSH 

horses. They were bright, active, and playful, Because of the large amounts of 

bran and sodium phosphate fed, the feces were soft. They were, however, formed 

and not liquid in consistency. Appetites were good and remained so throughout 

the 41-week experiment. 

During week 13 throzgb week 24 NSH 1 and NSH 3 showed no change. NSH 2 

developed an insidious shifting lameness accompanied by muscular stiffness and 

shortened stride. 

Table XVI. Weight gains in experimental nutritional secondary hyperparathy- 

roidism in horses 

Horse Initial Final Average gain 

weight, kg. weight, kg. kg./day 

NSH 1 195 

NSH 2* 205 

NSH 3 148 

Control 183 

300 

299 

280 

270 

* Final 14 days when NSH 2 could not rise are not included. 



0.37 

0.35 

0.46 

0.30

Clinical Observations 45 

During week 13 NSH 2 was observed dragging his left forefoot as the leg 

was moved forward. In addition, there was a hint of decrcased hock flexion while 

trotting. The lameness improved until 10 days later, when after exercise he came 

in lame on the left foreleg. Within a week, however, he was moving soundly and 

remained so until week 16. During week 15 hc slipped on a small patch of ice 

in the paddock and fell on his left side. No immcdiate 111 effects werc noted. Early 

in week 16 he became very lamc in his left rear leg. The limb was slightly pronated. 

When standing, the horse rested the leg most of the time. When moving he tended 

to carry the left hip higher than the right. The lameness improved somewhat. 

However, the colt looked incoordinated as well as lame. He would often walk 

with his right rear leg moving in the same path as his left front leg (“two track”). 

As he moved there was a rolling motion in his shoulders. His stride was shortened 

in all four legs. He wore his toes down. His heels grew long and his fetlocks 

became less angular. Trimming his feet helped correct the straight fetlocks. 

The other male colts began to mistreat him during play. In spite of his weight 

advantage he was too lame to protect himself, so he just rail away from them. 

Because of this he and NSH 3 were exercised in separate paddocks after week 16. 

Swelling of the mandible lateral to the cheek teeth was evident in NSH 

2 from week 16 on. Between week 16 and week 24 only a slight increase in the 

size of the mandible was noted. Percussion of the frontal and maxillary sinuses 

showed a progressive lack of density. At week 24 they sounded like cardboard 

in comparison with those of the control colt. The time of the appearance and the 

degree of severity of the clinical symptoms are summarized in Table XVII. 

During week 25 tbroigh tveek 36 the symptoms progressed in NSH 2. NSH 3 

developed symptoms similar to those shown by NSH 2 during the preceding 

12-week period. Both NSH 2 and NSH 3 began to have difficulties in rising. 

NSH 1 showed only vague symptoms of lameness. 

NSH 1 was the leader of the colts. When they were separated into two 

paddocks, he remained the leader of the control colt until week 28. At that time 

the control colt began to chase NSH 1 at will. NSH 1 was more muscular and had 

a considerable weight advantage but had difficulty making sharp turns. He became 

Table XVII. Clinical symptoms in experimental nutritional secondary hyperparathyroidism in horses 

Enlargement of Percussion Lameness 

Mandible Maxilla of sinuses Front Rear 

NSH horse no. 1 2 3 1 2 3 1 2 3 1 2 3 1 2 3 

Week 

6 

11 

16 

21 

25 

30 

34 

39 

- no symptoms; * mild symptoms; ** moderate symptoms; *** severe symptoms, 



46 Experimental Nutritional Secondary Hyperparathyroidism in the Horse . . . 

less inclined to play. IHe also showed a lack of freedom in moving his forelegs. 

At times his stride appearcd shortened and stilted. Percussion of his maxillary 

sinuses indicated a slight loss of density. 

NSH 2 became progressively worse. Some days he would hesitate to move. 

He did not play spontaneously and if chased around the paddock preferred to 

canter rather than trot. After this forced exercise he would stand trembling on his 

forelegs. He was lying down more than the other colts. In attempting to rise he 

would extend his forelcgs and start to spring to his fcet in a normal manner but 

fail in the attcmpt and sink back in sternal or fall in lateral recumbency. Two or 

three attempts were oftcn necessary before he rose to his feet. 

The mandibular cnlargcmcnt of NSH 2 progressed slightly, as did the 

“cardboard” sound on percussion of the maxillary sinuses. By week 34 the facial 

crcst seemed to bc less promincnt, cspecially rostrally. Thc face began to have a 

full appearancc, lacking sharp, bony angulations. The corner incisor teeth could 

be moved slightly by hand. 

NSH 3 bcgan to have trouble rising during week 25. tler movements with 

the forelegs became stiff and stilted. If forced to canter she moved with a peculiar 

“rabbit hopping” motion with her rear legs. The stiff, painful, and very short 

stride secmed to account for the hopping appearance. The progress of this lameness 

was similar to that of NSH 2. During week 28 NSH 3 was lame in her right 

foreleg. She would not play spontaneously. Pcrcussion sound changes of the 

frontal sinuses progrcsscd as in NSI-I 2. There was, however, no enlargement of the 

mandible or maxilla. 

During week 35 throzgh week 41 NSH 1 rcmained the same. He was destroyed 

during week 41. Early in week 40 NSH 2 was unable to rise. He had suffered a 

distal epiphyseal separation of the right radius. With the help of rope slings he 

could be placed on his feet but would stand by himself for just a few minutes. 

‘The area surrounding the distal radius was swollen and warm. The colt would 

not bear weight on his injured foreleg. Subsequently, dccubital sores and rapid 

weight loss occurred. He was dcstroycd during wcek 41. NSIH 3 showcd progrcs- 

sive difficulty in rising. IHer stride became shorter, stiffer, and more stilted, and 

she stumbled oftcn. Her toes wore down and her heels grew long. Percussion of thc 

maxillary sinuses indicated a progressive decrcase in bone density. Swelling was 

not evident in the mandible but was present to a mild degree in the maxilla. All 

her incisor teeth could be moved by hand. She was destroyed during weck 41. 

The control horse was vigorous and playful. His hoofs wore more evenly 

than those of NSIH 2 or NSH 3. No symptoms of lameness were noted. In general, 

his facial contours were much sharpcr than those of NSH 2 or NSH 3. He was 

destroyed during week 42. 

2. Clinico-pathologic Determinations 

The results of weekly determinations of phosphorus, calcium, and 

alkaline phosphatase levels of blood serum are presented in Charts 5 

through 8 (regression equations are given in the Appendix, Table 111). 

The results may be summarized as follows: 



Clinico-pathologic Determinations 47 

0 10 io io 40 6 b dD j, 4b 

Chart 5. Serum phosphorus in experimental nutritional secondary hyperpara- 

thyroidism. Phosphorus in mg per 100 ml on Y-axis, weeks on X-axis. NSH 1 

upperleft, NSH 2 upper right, NSH 3 lower left, control lower right. 



10. 


9. 

b I0 

12- 

10. 

.. 

20 33 40 

// 10, 

12. 

I I ’ 

10. 

9.. 

0 io 2.0 io 40 

12. 

.- 

- .. .. .D 

Chart 6. Serum calcium in experimental nutritional secondary hyperparathyroi- 

dism. Calcium in mg per 100 ml on Y-axis, weeks on X-axis. Experimental 

animals as in Chart 5. 



io 

i0

90. 

*. 

90. 90. 

70. / 

. 

Clinico-pathologic Determinations 49 

Chart 7. Total serum calcium and serum phosphorus product in experimcntal 

nutritional secondary hyperparathyroidism. Product on Y-axis, weeks on X-axis. 

Experimental animals as in Chart 5. 



... .. ... -

50 Experimental Nutritional Secondary Hyperparathyroidism in the Horse. 

6- 6. 

4’ 4. 

Chart 8. Serum alkaline phosphatase in experimental nutritional secondary hyper- 

parathyroidism. Phosphatase in sigma units on Y-axis, weeks on X-axis. Experi- 

mental animals as in Chart 5. 



(:linico-pathologic Determinations 51 

a) A diet with a calcium to phosphorus ratio of 1 : 3.68 immedia- 

tely caused hyperphosphatemia. 

13) Serum calcium first increased slightly and then decreased (NSH 

1 and NSH 3) or decreased immediately (NSH 2). Hyperphosphatemia 

and hypocalcemia progressed for about 10 weelis. 

c) Clinicopathologic evidences of hyperparathyroidism were 

manifest at the 11th week (NSH 1 and 3) or at the 13th week (NSH 2). 

At week 11 the serum P dropped in NSH 1 and 3. In NSI-I 2 this did 

not occur, but the progressing hyperphosphatemia was partly arrested. 

As the serum phosphorus started to decrease, a rise in serum calcium 

occurred. 

During the next phase, covering the period from week 12 to week 

23, serum phosphorus increased until it reached maximum and then 

decreased rapidly. During the same period serum calcium rose all the 

time, although compensation was not complete. 

At the end of this period the dietary calcium to phosphorus ratio 

was decreased from 1 : 3.68 to 1 : 6.19. Serum phosphorus then 

increased from week 23 through week 30, whereas serum calcium 

decreased during the same period of time. 

At week 30 the serum calcium reached its second minimum. The 

hyperparathyroidism now caused decreasing serum phosphorus and 

increasing serum calcium levels in all NSH horses. 

d) The product of total serum calcium and serum phosphorus 

described a triphasic curve over the experiment. The curves of these 

products were similar to those of serum phosphorus. The sequence of 

events was: 

i) Increase; hyperphosphatemia greater in degree than hypo- 

calcemia. 

ii) Decrease ; hypocalcemia of relatively greater degree than hyper- 

phosphatemia, which showed a temporary and partial compensation. 

iii) Increase; both phosphorus and calcium increasing; maximum 

product reached after 16, 20, and 20 weelis in NSH 1, 2, and 3, 

respectively. 

iv) Decrease ; hyperphosphatemia compensated for to a greater 

degree than hypocalcemia. In the middle of this phase the dietary ratio 

of calcium and phosphorus was decreased, resulting in increasing serum 

phosphorus levels but in still lower serum calcium levels; net result, 

thus, decreased product. 



52 Experimental Nutritional Secondary 1 lyperp~rathyroi~lisin in the IHorsc . . . 

v) Increase; serum phosphorus still increasing and hypocalcemia 

partly compensated for. 

vi) Decrease; hyperphosphatemia compensated for to a greater 

degree than hypocalcemia (with the exception of NSH 2). 

The regression lines described similar diphasic increase-decrease 

changes in all NSH horses. The magnitude and time periods were 

somewhat different in the horses, however. It should be emphasized 

that the increase-demase phases in ser/cnl alkaline phosphatase were inverse4 

related to the conti;rliioiu chanqes in semiin calciiiyN. 

3. Roentgenologic Observations 

A . Intrauital' Exaininatioii 

The results of the series of radiographs taken during the course of 

the experiment are summarized in Table XVIII. Progressive radio- 

lucency was evident in the mandibles (Fig. 18) and maxillae. Rc- 

companied by this, a radiolucent miliary mottling which might also 

be described as a spongy or moth-eaten appearance developed. Pro- 

gressive loss of the laminae durae was seen. Subperiosteal resorption 

appeared in the ventrodorsal views of the mandible on thecortical bone 

lateral to the roots of the corner incisor teeth. The characteristic changes 

in the metacarpi were endosteal roughening, radiolucent linear stria- 

tions in the cortex, and coarse trabeculation of the spongy bone at the 

metaphyseal ends of the medullary cavity. 

The changes in the mandibles and maxillae were observed sooner 

and progressed at a more rapid rate than those in the metacarpus. 

Although the changes noted in the affected colts were identical, the 

rates of change varied. NSH 2 showed the earliest change, NSJ-I 3 

next, and then NSI-I 1. The degree of change in NSH 1 was less than 

that in NSH 2 or 3. 

It must be noted that the changes were insidious and progressive, 

so that they did not become strikingly apparent from one month to the 

next. However, when 4 or 5 monthly radiographs were reviewed, the 

changes were obvious. 



Rocntgencilogic Observations 53 

Fie. 18. Ante-mortcin vcntrodorsal view of rostra1 end of inaiidihlc of control colt 

on right (u~cclc 28; age 14 months) and of NSH 3 on lcft (u,cck 40, age 16 months). 

Note lack (if dcvclopmcnt of laminae durac dcntcs around pcrinancnt central 

incisor of N S1 I 3 compared to control (arrou.) ; cndostcxl resorption and thinning 

of cortex in NSI I 3; loss of trahcculation and gcncralizcdradicilucciicy iiiNSH3. 

7 ahie XI ZZt. Expcrimcntal nutritional secondary hypcrparathyroidism in horses : 

R~~cntgeiiographic changes 

Wcck 

6 

11 

16 

21 

25 

30 

34 

39 

41 

Radioluccticy and tniliary Enciostcal roughening and linear 

mottling of mandiblc and radioluccnt striaticin in cortex of 

mas illa metacarpus 

NSI-I horse 110. 

NSI-I horse no. 

1 2 3 (:ontiol 1 2 3 Control 

- no change; * milcl change; *j: nioclcratc change; *':* sc\~cxc changc. 



54 Expcrimcntal Nutritional Sccondary I~lypcrparathyroiclism in the I-lorsc , . . 

F(y. 19. Post-mortem 1-cm-thick transvcrsc section through Icft maxilla at lcvcl 

of second molar. Control colt on right, NSI-1 2 on Icft. Note ci)inplctc resorption 

of laminae durac dcntcs and rarclicd widciicd maxilla in NSIi 2 compared to 

control. Compare zygo1iiaticc)inasillary suture in control and NSI-I 2. 

The control colt showed none of the changes seen in the affected 

colts. The even density of his bones throughout the experiment was 

used for comparison with. the texture of the bones of the affected colts. 

The radiographs taken at necropsy on bones freed of soft tissue 

and on the 1-cm.-thick bone slices were naturally more satisfactory 

than those taken during life. Increased radiolucency of bone was 



lioentgcnologic Ohscrvntions 55 

I,'(?. 20. Post-mortcm lateral vicu of rostra1 end of left mandiblc. Control colt 

upper, NSI-I 2 lo\vcr. Note radioluccnt iiiiliary mottliiia in NSll 2 comparcd to 

dcnsc cortical Ipattcrn in control, also cxtcnsivc resorption of Imnc surrounding 

incisor tccth in NSk 1 2 comparcd to control. 

generalized throughout the head, ribs, and limbs (the vertebral column 

and pelvis were not radiographed). These changes were similar to 

those seen during life but much more clearly defined. The contrast 

between the teeth and surrounding bone was striking (Fig. 19). The 

cortical bone along the ramus of the mandible in NSH 2 was mottled 

and thinned to the point of nonesistence. The mandibular canals in 

NSf I2 and 3 blended with the surrounding bone in sharp contrast to 

the control's mandible, in which the canal was clearly defined. There 

was also a loss of contrast between diploe and lamina in the roof 

of the cranium. The bone had a radiolucent moth-eaten appearance 

(Figs. 19 and 20). 

The cortices of the 1-cm.-thick transverse sections from the mid- 

diaphysis of the long bones were radiolucently stippled throughout 

(Fig. 21). There was also a radiolucent mottled appearance in the 

endosteal area, becoming less evident toward the periosteum. In some 

cases the periphery of the medullary cavity had a distinct scalloped 

appearance (Fig. 21). 



56 Experimental Nutritional Secondary 1 lyperp~~ithyroi~listn 111 the I Jorse 

Fig. 21. Post-mortcm 1-cm-thick cross scction from diaphysis of left metacarpus. 

NSH 3 011 Icft, control on right. Note cndostcal roughening in NSIH 3 comparcd 

to sharp corticomcdullary junction. in control, also thin cortex of NSH 3 and 

generalized radio1uccn.t stipplcd appcarancc compared to contrc)l. hlctacarpal 11 

shows thc satnc changcs. 

Fi’. 22. Post-mortcm 1-cm-thick longitudinal scction i)f right rih no. 10 at 

costochoiidral junction.. NSH 3 on left, control on right. Early rcsi)rption cyst is 

present in NSI-I 3. Cortex of NSH 3 is thin, mottled, and at some points ohlitcrated 

compared to ci)ntrol. 

Radiographic evidence of cysts within bones was not common. 

The costochondral junction of rib 10 on the right side of NSH 3 con- 

tained one large resorption cyst approximately 8 mm. in diameter 

(Fig. 22). Only ribs 3 and 10 on the right side were radiographed. 

The proximal epiphyseal line of the radius in NSI-I 2 and 3 was 

widened at scattered points projecting 2 to 3 mm. into the metaphysis. 

The epiphyseal lines of the humerus, femur, and tibia showed similar 

but less advanced changes. 



Pathologic Anatomy 57 

7bb/e XIS. Size atid \\eight of uppcr parathyroid glands in nutritional secondary 

hyperparathyrcjidisiii in horses 

Size tiitn. Rclativc weight 

1 .eft Right Weight iiig. iiig./kg. 

body \\eight 

XS11 1 121 7. 4 102. 10x4 413 1.38 

NSII 2 15i. 10x 4 15x 8x 6 712 2.61 

NSII 3 61 6\\ 4 9 x 7 :.: 4 280 1.03 

(:ontrol 6;. 6~ 3 6x 4 x2 130 0.48 

hican relative \\eight for NS11 horses: 1.67 1 0.48. 

Ilciicc, 1.67-2x 0.48 (s.c.m.)>0.48 (valuc of control horse). 

The control colt's bones were in marked contrast with those of 

the affected animals; they completely lacked the changes seen in the 

bones of the diseased animals (Figs. 18-22). 

4. Pathologic Anatomy 

The nutritional condition was good in all four animals. 

Each colt showed a mild gastric myiasis (G'as/rophihs spp.) and a 

mild intestinal ascariasis (Parascaris eqmrum). Otherwise gross changes 

were present only in the parathyroids and the slieleton. 

a) 1'arathyroid.r 

The size and weight of the upper parathyroids are summarized in 

Table XIX. 

The glands of all four colts had a finely lobulated external 

appearance. The cut surface of glands of the control horse and NSI-I 1 

maintained a lobulated appearance, whereas it was smooth and more 

evenly filled with parenchymal tissue in NSIH 2 and 3. 

11) .I'ke/CtOJ7 

NSH 1. No gross lesion was noted. 

NSH 2. The face had a swollen appearance. The facial crest 

blended diffusely into the moderately swollen maxilla so that the 

anterior extremity of the crest was hardly visible. The consistency of 



58 Experimental Nutritional Sccondary Hyperparathyroidism in the Ilorse . 

the maxilla was softer than normal. The cut surface of the maxilla 

yielded to finger compression, and a blood-tinged fluid oozed from the 

cut surface. The lateral aspect of the mandible just below the gingival 

border was moderately thickened. 

Ribs 8, 9, and 10 on the right side showed a transverse fracture 

halfway between the costochondral junction and the head of the ribs. 

A fibrous callus around the fracture caused a spool-shaped enlargement 

of the area. There were no hemorrhages around the fractures. Other 

ribs could be bent 90 degrees without breaking. Under further bending 

these ribs broke like cardboard rather than snapping like normal ribs. 

The right radius presented a complete distal epiphyseal separation 

but the epiphysis and diaphysis were well aligned. Subperiosteal hemor- 

rhages were present for a short distance on the diaphysis. Soft tissue 

surrounding the epiphysis was swollen with hemorrhagic edema. 

NSH 3. The cut surface of the maxilla yielded to finger compres- 

sion in a manner similar to NSH 2. The tissue surrounding the tooth 

buds of the permanent premolars was red in color, of a very loose 

consistency, and cut easily with a necropsy knife. The incisor and pre- 

molar teeth could be moved by hand in their alveoli. 

The costochondral junction of rib 10 on the right side was loose. 

A cyst 8 mm. in diameter, filled with a hemorrhagic, semigelatinous 

fluid, was present at this junction. Other ribs were similar to those of 

NSH 1 and 2 but exhibited no fractures. 

B. Microscopic Exanhation 

a) Parath_yroids 

Inberstitiivn. The parenchyma to interstitium ratio in the para- 

thyroid glands is given in Table XX (for analysis, see Appendix, 

Table IV). The interstitium was less prominent in all NSH horses than 

in th.e control and the normal material as presented in Chapter I. 

Because of the small number of experimental animals, these differences 

were not statistically significant. Fig. 23 from the control horse and 

Fig. 24 from NSH 2 are representative of the difference. The relatively 

large interstitial fat spaces present in the parathyroid gland of the 

control horse were never observed in NSH horses. The microscopic 

field was, instead, more filled in. The capillary network was abundant 

which, of course, influenced the parenchyma to interstitium ratio. 




fhb/c. A’X. Espcrirncntal nutritional sccondary hypcrparathyroidism in horses: 

I’arcnchqma to intcrsritium atid epithelial cytoplasm to nucleus ratios and nuclcar 

surfacc sixs of parathyroid 

I Iorsc I’arcnchyma/ 

interstitiurn 

x * s. c. Ill. 

NSI-I 1 6.72 1: 0.46 

6) 

NSlH 2 7.7s I 1.00 

(11 ~ 6) 

NSI-I 3 6.19 k 0.79 

(n ~ 6) 

Control 5.72 -1: 0.58 

(11 ~ 6) 

Cytoplasm/ 

nuclcus 

x 3- s. c. in. 

5.07 j 0.43 

(11 6) 

6.09 0.25 

(n ~ 6) 

5.24 1 0.59 

(11 6) 

5.65 1 0.46 

(11 6) 

Nuclear surfacc 

plariimctcr units 

x 3: s. c. in. 

36.88 j 0.69 

( (1 100) 

39.67 1 0.73 

(n 100) 

41.21 I 0.92 

(I1 ~ 100) 

22.59 I 0.52 

(I1 100) 

Embryologic rudiments were present in all sections from all 

horses. Thymus rudiments were very prominent in NSH 1, less outstanding 

in NSH 2 and the control, and absent in NSH 3. Cystic 

dilatation of large ICURSTEINEK’S canals were observed at the parathyroid 

hilus of NSI-I 3 and the control. 

I-’arenc,$~~nta. In the control horse the light chief cells predominated, 

although fairly large areas of dark chief cells (Fig. 23) were also present. 

In the NSH horses the light chiefcells again predominated. They were, 

however, much larger than normal light chief cells. Table XX (for 

analysis, see Appendix, Table IV) shows that the nuclear surface of the 

light chief cells of NSH horses was significantly larger than that of the 

control horse and of the normal horses of Chapter I. The cytoplasm to 

nucleus ratio was the same in all horses. It can thus be concluded that 

the light chief cells of NSI-I horses were hypertophic. The tinctorial 

properties of the cytoplasm were the same as those described for light 

chief cells in the normal material, whereas the nucleus was more 

intensely basophilic. 

Dark chief cells did not occur in NSFI horses. 

Water-clear cells were much more numerous in all NSH horses. 

They occurred in small islands or in large areas (Fig. 25). Both small 

and large water-clear cells were present. Intermediate stages between 

light chief and water-clear cells were frequently observed. With 

cresylecht violet the cytoplasm of the light chief cells stained diffusely 

and rather deeply blue. Juxtanuclear bodies were common in these 

cells. In intermediate stages the basophilic material was present in thin, 



(10 Lxpcrimental Nutritional Sccondary ~lypcrparathyroidism in the I lorse , . . 

irregular flakes, often pushed toward the periphery. Clear irregular 

areas were left in the cytoplasm after such coalescence of the basophilic 

material. At this stage the juxtanuclear bodies were much more 

frequent in the intermediate cells than in the light chief cells. Two, 

three, or even more bodies could be present in the cytoplasm. Some- 

times they were actually located next to the nucleus, but their distribu- 

tion was quite haphazard. They were often located next to the cell 

membrane. In cells more definitely of the water-clear types, the baso- 

philic material was further pressed together and appeared to be glued 

to the cell membrane. It gave a false impression of a very thick cell 

membrane. With the cytoplasm otherwise empty the very frequent 

juxtanuclear body or bodies stood out well (Fig. 26). 

Table XX (for analysis see Appendix, Table IV) shows that the 

nuclear surface of the light chief cells varied significantly in the NStl 

horses. As there were no significant differences in the cytoplasm to 

nuclear ratios, it can therefore be concluded that the degree of hyper- 

trophy of the parathyroids varied in the NSH horses. 

Epithelial fat was not demonstrated in the parathyroids of NSH 

horses or of the control. 

The diagnosis to be applied to the changes in the parathyroid 

glands of NSH horses requires some analysis. As shown in Table XIX, 

the glands were grossly enlarged. There were no differences in the 

relative amounts of interstitial tissue including embryologic rudiments. 

/,/,q. 27. I’arathyroid, coiitrol. Jmgc area of interstitial fat. hlostly light chief cells; 

area of dark chief cell (in front of arrovrr). El & E, x 80. 

/;(’. 24. I’arathyroid, NSIH 2. Interstitial fat spaces rcplaccd by parcmcliynia 

consisting mainly of light chief cells ; areas of watcr-clcar cells (arrows). Abund;uit 

capillary network. 1-1 h E, x 80. 

1;i.r. 25. l’arathyroid, NSIH 1. I.ight chief cells in upper left third of picture; 

otherwise water-clear cells. Coalcsccncc of cytoplasmic RNA with flakes in 

cytoplasm (long arrow) or glued to the cell mcmhranc (short arrolv). 1-1 & E, oil 

itnmcrsion, Y 720. 

f(q. 26. I’arathyroid, NSI-1 2. Nurncrous justanuclcar bodies \\.it11 haphazard 

distribution: at short thin arrow nest to the nucleus; at incdiuni short thin arro\\. 

in the middle of the cytoplasm; at long thin arro\y at thc cell membrane. At 

straighi thick arrow intcrmcdiatc stage Ixtwccn light chief acid \i,:itcr-clc:ii- cell : 

at curved arro\r water-clear ccll. Crcsylccht violet, x 450. 





61

62 Expcrimcntal Nutritional Secondary I-Jypcrparathyroiclism in the Horse 

7'a0/(' /YAY]. Weight increase of upper parathyroid glands in relation to ccllular 

hypertrophy 

I-lorsc Relative weight Volumetric increase 

of parathyroids due to hypertrophy 

NSI-I 1 2.14 u C 1.99 x c 

NSM 2 5.44 x c 2.37 > C 

NSII 3 2.88 / C 2.58 ,-' C 

(:olltrol (1 c 

There was, therefore, an actual increase in parenchymatous tissue. It 

has already been demonstrated that the light chief cells were hyper- 

trophic. Wheter or not this hypertrophy alone can explain the enlarge- 

ment of the glands must now be considered. Table XXI shows how 

many times greater the relative parathyroid weights were in NSH 

horses than in the control. The volumetric increase due to hypertrophq 

is expressed in the same way. The figures of the volumes were obtained 

by multiplying the figure of the nuclear surface by a factor r3/+ ( = r, 

the mean radius of the nucleus). Thus Table XXI shows that the hyper- 

trophy alone cannot explain the enlargement of the glands. It was 

therefore concluded that a hyperplasia of the parathyroid glands was 

also present in the NSI-I horses. 

f*g. 27. (.ontrol. : 45. 

Fiq. 29. NSI-I 1. Alandihlc. Ostcitis tibrosa. Ostcoclasts in Howship's lacunae 

(straight arrow) or flattened along the bone. Ostcoblastic apposition on opposite 

side of trabccu.lac (untilled arrow). Poorly collagcnized fibrous tissue replacing 

rcsorbcd bone. 14 & G. r 120. 

F;,y, 30. NSH 1. hlasilla. Osteitis tihrosa. All old bone rcsorhcd. Onc largc 

ostcoclast with pyknotic nuclci left (arrow). Vivid ostcoblastic activity with 

abundant nontnincr.alizcd ostcoid. Fibrous tissue replacing rcsorhcd bone. I4 ct E, 

Y 250. 





63

64 13xpcrimcntal Nutritional Secondary I-lypcrparathyroidism in the Horse. . . 

I?) .Skeleton 

Osteoclastic resorptioii. Resorptive processes were demonstrated in 

every bone section from every NSfl horse. Although generalized in 

nature, there were sites of predilection where the changes were more 

pronounced, viz., cancellous bone of the skull, cancellous bone of the 

ribs and metaphyses of long bones, other cancellous bone, outer 

circumferential lamellae of long bones, HAVBRSIAN systems of compact 

bone including compact bone coating cancellous bone, and interstitial 

lamellae of compact bone. 

A cross section of the mandible just behind the last molar tooth 

of the control horse is shown in Fig. 27. The resorption in the same 

area of the mandible of a NSH horse was very advanced, as is shown in 

Fig. 28. Practically all bone was resorbed. Only small fragments of old 

bone remained, and such spicules were the sites of osteoclastic 

resorption. 

The changes in the maxilla were equally severe. Relatively few 

trabeculae remained, and these were the sites of vivid osteoclastic 

resorption (Fig. 29). Deep excavations into trabeculae and more superficial 

HOLYSHIP’S lacunae containing osteoclasts and osteoclasts 

flattened along trabeculae were frequently encountered. In other areas 

in the maxilla the resorption was complete with no old, mineralized 

bone left (Fig. 30). 

Other skull bones showed similar changes, although not so 

advanced. 

Fly. 31. NSI 1 2. Ostcoblastic apposition. Abundant nonmineralized osteoid. 

FI & E, x 160. 

Fq. 32. Control. Humerus diaphysis, cross section of cortex. 1-1 & E, x 130. 

I’olariicd light. 

J;i

Pathologic Anatoiny 



65

66 Experimental Nutritional Sccondary 1-lypcrparathyroidism in the Iiorsc. . . 

The osteoclastic resorption of cancellous bone in the ribs was very 

striking. Most trabeculae presented numerous HOV~SHIP'S lacunas, 

usually containing osteoclasts. 

A cross section of the cortex of the humerus in the control horse 

showed the structure presented in Fig. 32. In this particular field 

HAVERSIAN canals were all comparatively small, as were VOLKMANN'S 

canals. Apposition and resorption were at a virtual standstill. This was, 

however, not the rule in the bones of the control horse. Resorptive 

processes were commonly observed, especially toward the endosteal 

aspect, and the formation of osteons was still more marked. 

In NSH horses the imbalance between resorption and apposition 

in favor of resorption was very striking. Resorption always originated 

in HAVERSIAN and VOLKSMANN'S canals. In the earliest stages small 

osteoclasts with only two or three nuclei were found flattened along 

the innermost internal lamella of HAVERSIAN systems. Resorption was 

first very regular, and it appeared that lamella after lamella was resorbed 

stepwise. Later on when resorption reached more peripheral lamellae, 

several osteoclasts could be observed within the widened HAVERSI AN 

canal and the erosion of the lamellae became more irregular. Typical 

HOTVVSHIP'S lacunae with osteoclasts (Figs. 33 and 35) occurred, and the 

indentations into the bone concerned several lamellae (Fig. 36). 

F/




68 Expcrimcntal Nutritional Secondary I-Iypcrparathyroidism in the tIorse . . . 

The resorption from VOLKMANN’S canals was liliewise very inconspicuous 

in the beginning. In more advanced stages the widening 

of the canal could be impressive (Figs. 33,34 and 37). As the resorption 

from VOLKMANN’S canals proceeded, the disruption of lamellae of 

HAVERSIAN systems became very prominent (Figs. 34 and 36). Osteoclastic 

resorption of interstitial lamellae occurred, it appeared, only as a 

result of lateral expansion of resorptive processes originating in 

HAVERSIAN and VOLKMANN’S canals or subperiosteallg (Figs. 34, 36, 

38, and 40). 

Longitudinal sections of compact bone showed that the resorption 

was very irregular. The width of the HAVERSIAN canals varied within a 

wide range, and localized encroachment upon adjacent osteons and 

interstitial lamellae was frequently encountered. 

The outer circumferential lamellae of compact bone were also 

sites of resorption. The normal structure (Fig. 39) was never present in 

NSH horses, and in most sections there were hardly any remnants of 

such lamellae (Fig. 40). Resorption usually expanded into adjacent 

osteons and interstitial lamellae (Fig. 40). In other instances a haphazard 

resorption was going on, and numerous lacunae filled with osteoclasts 

were then observed. The resorption was often found to be very much 

accentuated locally with large excavations into the compact bone and 

loss of the osseus support of the periosteum (Fig. 38). 

The morphology of the osteoclasts varied. Actively eroding 

osteoclasts were usually present in HOWSHIP’S lacunae (Figs. 29, 33, 

35, 38) or flattened along trabecular (Fig. 29). Their shape varied 

accordingly ; in the former case they were irregularly rounded, in the 

latter elongated. The nuclei were relatively large and diffusely scattered 

throughout the cells. In areas where mineralized bone was no longer 

available for resorption, the nuclei of the osteoclasts were pyltnotic and 

retracted centrally or toward one end of the cell (Fig. 30). Inactive 

osteoclasts trapped in fibrous tissue sometimes showed vacuolization 

of the cytoplasm. In rare instances a phagocytized erythrocyte was 

seen in osteoclasts in hemorrhage areas in loose connective tissue. 

Fibrosis. The fibrous tissue replacing the resorbed bone varied 

considerably in tinctorial properties in different areas. In the jawbones 

it was rather well collagenized with a deep-red staining reaction with 

van Gieson. Differences in collagenization of the fibrous tissue did 

occur, however, in areas of long-standing resorption. The fibrous 

tissue replacing the resorbed outer circumferential lamellae was usually 

well collagenized (Fig. 37), but the birefringent material (Fig. 40) 




Fiq. 37. Control. Humerus diaphysis, cross section showing outer circumferential 

lamellac (right). 1-1 & E, original magnitication x 120, cnlargcd 1.7. Polarized light. 

Fj-q. 40. NSH 3. l~lutncrus diaphysis, cross secrion. Outcr Circumferential lamellac 

cotnplctcly resorbed, replaced by irregularly bircfringcnt fibrous tissue (right). 

Adjaccnt osteon under resorption with disruption of lamellac (straight arrow). 

Resorption of interstitial latnellae (curved arrow). I3 C(c E, original magnification 

x 120, enlarged 1.7. Polarized light. 

indicated a rather irregular structure in the connective tissue. The 

fibrous tissue replacing bone resorbed from HAVERSIAN and VOLK- 

brmN’s canals (Figs. 33-38,40) was of another nature. It was poorly or 

not at all collagenized, as evidenced by very little affinity for van 

Gieson’s stain. 

F1emorrbuge.s. Hemorrhages in the connective tissue replacing 

resorbed bone occurred only in the jawbones, the nasal bone, and the 

ribs close to the costochondral junction. The hemorrhages were very 

small. Those associated with the rib fractures and the epiphyseal 

separation of the radius in NSH 2 were more extensive. 



70 Expcrirnental Nutritional Secondary Hyperparathyroidism in the I-Iorse . . . 

Hemosiderosis. Hemosiderin in macrophages of the connective tissue 

were present in the maxilla and the mandible of all NSH horses, but it was 

rare. Hemosiderosis of osteoclasts was observed in very rare instances. 

Brown nodes. Clear-cut examples of brownnodes werenot recorded. 

At the site of the fracture of the eighth right rib of NSH 2 a picture 

somewhat similar to a brown node did occur, but the hemorrhages, 

hemosiderosis, and accumulation of giant cells were believed to be 

associated with the fracture rather than with osteitis tibrosa per se. 

Cj~ts. Microscopic cysts were of rare occurrence in the jawbones 

and absent elsewhere. They appeared to be derived from hemorrhages 

rather than from mucoid degeneration. 

Osteoid apposition. Osteoblastic activity was observed in cancellous 

as well as in compact bone. In the jawbones, where the resorption was 

most advanced, osteoid bars of different thicknesses and of haphazard 

distribution were quite common (Figs. 28, 29, and 30). Osteoblasts 

were usually present in a single layer. Most of these bars stained 

diffusely pink with hematoxylin and eosin, and the deep-purple center 

seen in old bone was not present. Osteoclasts were absent along or 

within such osteoid bars. On the other hand, highly active osteoclastic 

resorption with the formation of numerous HOWHIP’S lacunae 

and deep excavations into trabeculae was frequently observed occurring 

simultaneously with apposition on the other surface of the same trabeculae 

(Fig. 29). 

Osteoid formation along the trabeculae of ribs was likewise rather 

pronounced (Fig. 31) with osteoblasts sometimes present in several 

layers. As before, the osteoid was light pink in color with hematoxylin 

and eosin. 

The formation of new osteons in areas of previous resorption was 

frequently observed in cortical bone (Figs. 33,34,37, and 38). Lamellae 

were laid down in an orderly manner, and a single layer of osteoblasts 

was usually present internally. 

All NSH horses exhibited the changes just described. The degree 

varied somewhat, however, NSI-I 2 presented the most advanced 

changes, then NSI-I 3, and finally NSH 1. 

Morpbologic diagnosis: GeneraliTed osteitis jbrosa. 

c) Other Tissues 

No changes were observed in any other tissues. There was no soft 

tissue calcinosis. 



V. Experimental Nutritional Secondary Hyperparathyroidism 

in the Horse: Discussion 

1. Clinical Course 

The clinical symptoms observed in NSH horses agreed in general 

with those of earlier descriptions (see Chapter 11). The time of onset 

differed, however. This will be discussed later under the bone changes. 

2. Serum Phosphorus, Calcium, and hlltaline Phosphatase 

Interpretation of the changes in serum phosphorus and calcium 

and of the product of total calcium and serum phosphorus requires 

appreciation of two facts: 

i) Serum calcium and phosphorus are interrelated according to 

the law of constant ion product in a saturated solution at a given pH: 

Ca++ x HP04-- 

CaHP04 

= kpFI 

(“this being the only logical means of correlating calcium and phosphorus”-T~o~so~ 

and COLLIP, 1932). 

ii) The solubility of calcium and phosphorus in the blood serum 

increases in hyperparathyroidism. 

The importance of additional effects of the parathormone such as 

resorption of bone and increased renal excretion of phosphorus is 

self-evident. 

The interrelationship between calcium and phosphorus in the 

blood serum has long been a question of debate. COLLID (1926) showed 

that, following injections of parathormone at 4-hour intervals into 

dogs, serum calcium rose from 12 to about 20 mg. per 100 ml. and that 

whole blood phosphorus increased, after a slight initial decrease, from 

6 to 13 mg. per 100 ml. Similar results were reported by THOMSON and 

PTJGSLEY (1932), LOGAN (1939), MCLEAN et al. (1946), and others. 



72 Expcrimcntal Nutritional Sccondary Hypcrparathyroidism in the Horse. . . 

It would seem, therefore, that an inverse relationship between 

calcium and phosphorus should not exist. An experiment by MCLEAN 

et al. (1946) offered the explanation. They introduced the term “biological 

solubility” and defined undersaturation, saturation, and supersaturation 

of calcium and phosphorus in blood serum on the basis of 

this term. “The limit of biological solubility is the point at which 

deposition of the bone salt just occurs in the matrix of rachitic cartilage 

in vitro.” Levels above this point were considered supersaturated and 

below this level undersaturated. MCLEAN et al. performed the following 

experiment: Adult dogs whose serum did not mineralize rachitic 

cartilage in vitro were given a large dose of parathormone at 0 and at 

4 hours. The serum calcium rose rapidly and leached maximum level 

after 12 hours. A concurrent but slight rise in the serum phosphorus 

level was also recorded. At 4 hours the serum induced a slight mineralization 

of rachitic cartilage in vitro. After 8 hours the ion product of 

calcium and phosphorus of blood serum and in vitro mineralization 

tendency was still higher. They concluded, then, that at 4 hours the 

serum must have been at least saturated and, after 8 hours, supersaturated. 

According to these authors, the cause of supersaturation 

must be sought in the active intervention by the parathyroid hormone 

because “there is no way in which a solution of a salt, in contact with 

a solid phase, may become supersaturated by simple equilibrium with 

the solid”. 

The reports just mentioned concerned the interrelationship 

between calcium and phosphorus in noncompensatory, exogenous 

hyperparathyroidism. The results indicate, therefore, the effects of the 

parathyroid hormone on serum calcium and phosphorus. The interrelationship 

between calcium and phosphorus can be better demonstrated 

in the reverse condition, viz., the effect of different levels of 

serum calcium and phosphorus on the parathyroid glands. HAM et al. 

(1 940) showed conclusively that “hypocalcemia, instead of hyperphosphatemia, 

is the primary cause of physiological hypertrophy of 

the parathyroid glands”. Their results were confirmed by PATT and 

LUCKIIARUT (1942), STOERK and CARNES (1945), and EWGFELDT et al. 

(1954). Different ways have been employed to produce hypocalcemia 

leading to secondary hyperparathyroidism. I-IAM et al. simply underfed 

calcium to induce hypocalcemia, PATT and LUCKHARUT lowered serum 

calcium by intravenous injections of sodium oxalate, and COPP et al. 

(1962) used EDTA injections. With all these methods serum calcium 

alone was influenced, and regardless of the method the result was, as far 



Scruin Phosphorus, Calciiiiii, and Alkalinc l’hosphatnsc 73 

as the product of calcium and phosphorus is concerned, an /iiidwsut/irated 

serum. There is no reason to expect that a primary decrease in 

either ion would increase the other. On the other hand, a primary 

increase in either ion will decrease the other when the saturation point 

is reached. Experimental hyperparathyroidism due to hypocalcemia 

following excessive phosphorus feeding with continuous analyses of 

serum calcium and phosphorus has been reported in the swine and rat. 

LIEGEOIS and DERIVALJX (1951) fed pigs diets with calcium to 

phosphorus ratios varying from 1 : 5.5 to 1 : 11.6. Serum phosphorus 

rose from the second week through the fifth week and then fell to and 

remained within normal range. At their height serum phosphorus 

levels of close to 11 mg. per 100 ml. were recorded as compared to the 

initial 6.5. Serum calcium remained within normal range for 2 or even 

5 weelis, then dropped as low as 6.5 mg. per 100 ml. in one case. 

Normalization occurred after 7 to 8 weelis. Hyperphosphaturia occurred 

a short time after the highest serum phosphorus and the lowest serum 

calcium levels had been observed. Thisexperiment showed the intimate 

relationship between serum calcium and phosphorus. Excessive phosphorus 

feeding resulted in hyperphosphatemia and, after some ddq, 

during which period saturation of serum occurred, serum calcium fell. 

Once the hyperparathyroidism was induced by hypocalcemia, the 

effects of increased parathyroid hormone levels influence the relationship 

between serum calcium and phosphorus, i.e. release of bone 

mineral, increased solubility of calcium and phosphorus in blood 

serum, and increased renal excretion of phosphorus. 

Supersaturation does not invalidate the law of constant ion product. 

In later stages when hyperphosphatemia is partly or completely 

compensated for, or even overcompensated for, the ion product may 

not reach saturation. Changes in one ion are then not reflected in the 

other, but this, of course, does not contradict the reciprocity of calcium 

and phosphorus in a saturated solution. 

ENGFELDT et al. (1 954) induced secondary hyperparathyroidism in 

rats by feeding diets with excessive amounts of phosphorus in proportion 

to calcium. They stated, “In our experiment it has not been possible 

to confirm the existence of a direct correlation between the content of 

calcium and phosphorus in the diet and the concentration of these 

substances in the blood. Further, it can be concluded that there is no 

inverse relationship between the blood-calcium and the blood-phosphorus, 

as has, previously, been pointed out by others”. Morphologic 

evidences of parathyroid hyperactivity were observed in rats after 60 



74 Experimental Nutritional Secondary Hyperparathyroidism in thc Horse. . . 

days on a diet with a calcium to phosphorus ratio of 1 : 16, with 

calcium malting up 0.125% of the diet. Because of hyperparathyroidism 

the initially occurring hyperphosphatemia was overcompensated 

for. In normal rats the product of total serum calcium and phosphorus 

was 52; after 60 days on the experimental diet this product was 37.4, 

i.e., an undersaturation. A relationship referring to a condition in a 

saturated solution cannot be discarded for the reasons given. Further, 

if we do not accept an interrelationship between dietary calcium and 

phosphorus on one hand and serum calcium and phosphorus on the 

other, as well as an inverse relationship between phosphorus and 

calcium in saturated blood serum, then the dietary ratio of these elements 

would be of no importance. It certainly is important, however. 

In the three NSH horses of the present study the close relationship 

between serum calcium and phosphorus was demonstrated. The 

relationship was very obvious both in the initial period of the experiment 

when the hyperparathyroidism was being induced, as well as in 

later stages when the actions of the parathormone complicated the 

picture. During the first 10 weelis serum phosphorus rose and calcium 

fell. After 10 weeks the effects of hyperparathyroidism appeared. The 

hypocalcemia was gradually compensated for, but the pre-experimental 

levels were not regained. This period lasted 12 weeks, i.e. as long as 

the dietary calcium to phosphorus ratio was consistently kept at 

1 : 3.68. During this period the serum phosphorus went down, up, 

down. The explanation for the decreasing serum phosphorus levels 

seems to be obvious. The fall is due to the increased renal excretion of 

phosphorus afzd to the increasing serum calcium. In the middle of this 

period, when serum calcium was steadily rising, there was a sharp 

increase of serum phosphorus as well. This increase in serum phosphorus 

went on for 8, 7, and 3 weeks, respectively, in the three NSH 

horses. This may appear to be an insurrection against the law of constant 

ion product; it is not, however. Here the action of the parathyroid 

hormone discovered by MCLEAN et al. (1946) entered the picture; 

the serum became supersaturated. 

At the end of this period the imbalance between calcium and 

phosphorus in the diet was made still greater. Once more the direct 

action on serum phosphorus of increased phosphorus intake was 

demonstrated, and once more the inverse relationship between serum 

phosphorus and calcium was shown. During all this last period the 

serum must be considered to have been supersaturated (see below) 

under the influence of increased parathormone levels, but the inverse 



Serum Phosphorus, Calcium, and Alkaline Phosphatase 75 

relationship between serum calcium and phosphorus was still very 

obvious. 

In the analyses of the solubility of calcium and phosphorus in 

blood serum the total values of these elements were used. MCLEAN and 

URIST (1 961) commented upon this empirical product, introduced by 

HOWLAND and KRAMER (1921), as follows: “Moreover, since the proportions 

of Ca++ and HP04-- to the total Ca and total P are relatively 

constant, HOWLAND and KRAMER’S empirical formulation, Ca x P, is 

as reliable as the ion product itself, or as the product of the activities of 

the ions.” 

The product of total calcium and phosphorus in blood serum 

showed that, in this respect, the changes in serum phosphorus were 

more decisive than those in serum calcium. The regression lines of the 

products were quite similar to those of serum phosphorus. The increase 

in the product reached remarkable heights. At the highest levels 

the products were 43, 57, and 38% higher in the three NSH horses, 

respectively, than in the control horse. As the blood serum is normally 

almost saturated [ALBRIGHT and REIFENSTEIN (1948), in man], at least 

the highest values must indicate supersaturation in the sense of 

MCLEAN et al. (1946). Even at the end of the experiment, when there 

was a partial compensation for the serum phosphorus and calcium, the 

products remained at levels 18, 19, and 19 yo, respectively, higher than 

in the average of the control. 

The degree of hyperphosphatemia was not the same in the NSH 

horses. It was most severe in NSH 2, then NSH 3, and, last, NSH 1. 

Horses NSH 2 and 3 were given dibasic sodium phosphate and NSH 1 

monobasic sodium phosphate, but regardless of the source the imbalance 

was made the same. With only three experimental horses and 

no data on blood and urine pH and so forth, we will not attempt to 

discuss what caused the differences in hyperphosphatemia. The important 

point is that the degree of hypocalcemia and therefore the degree 

of parathyroid hyperactivity (Table XlI, for analysis see Appendix 

Table IV) and of roentgenologic changes was a direct function of the 

degree of hyperphosphatemia. 

Serum alkaline phosphatase. ALBRIGHT and REIFENSTEIN (1948) 

stated: “In the absence of any other cause for a higher phosphatase 

level such as liver disease or obstructive jaundice, a high serum phosphatase 

level is probably indicative of increased osteoblastic activity.” 

With regard to the cause of the increased osteoblastic activity in hyperparathyroidism 

they wrote: “As the bones become weak they will be 

7 Krook/Lowe 




more subject to stresses and strains ; this will stimulate the osteoblasts 

to lay down more osteoid tissue.” The level of serum alkaline phosphatase 

would therefore be “an index not of the degree of hyperparathyroidism 

but merely of the degree of bone disease”. Concerning the 

alkaline phosphatase MAJNO and ROUILLER (1951) wrote : “Although 

theories concerning the mode of action have varied somewhat, the 

phosphatase remains the undisputed calcification enzyme” (free translation 

from the original German). 

As shown in Charts 6 and 8, an inverse relationship between 

serum calcium and serum alkaline phosphatase was demonstrated in 

all NSH horses, although the maximums and minimums of serum 

alkaline phosphatase were somewhat delayed compared to the 

minimums and maximums of serum calcium. The continuous changes 

described diphasic curves beginning, in the case of calcium, with a 

decrease and, in the case of alkaline phosphatase, with an increase. The 

initial increase of serum alkaline phosphatase, progressing over 18, 11, 

and 16 weeks in the three NSH horses, respectively, would theoretically 

be explained by the function of alkaline phosphatase as the 

calcification enzyme. The stresses and strains on the skeleton, weakened 

by resorption, would stimulate increased osteoblasticactivity in accordance 

with the quotation from ALBRIGHT and REIFENSTEIN. Such an 

explanation seems very unlikely. First, roentgenologic signs of 

resorption were evident only after 21, 11, and 21 weelis in the three 

NSH horses, respectively. Second, the mode of action of the parathyroid 

hormone on the osteoblasts is a depression [GAILLARD (1961)l. 

The stimulus from stresses and strains for osteoblastic activity would 

then have to overcome this action of the parathyroid hormone at this 

early time also. Third, even if the increased serum alkaline phosphatase 

levels were to be explained as evidence of increased osteoblastic 

activity, the value of such an explanation is definitely nullified by the 

sabseqzlent decrease in serum alkaline phosphatase. The demand for 

increased apposition could not possibly be lowered in any phase of the 

experiment, especially not in the last stage when radiologic, clinical, 

and morphologic changes were very dramatic. 

The explanation for the diphasic changes in serum alkaline phosphatase 

is rather to be found in the work by RUTISHAUSER and his 

associates. RUTISHAUSER and MAJNO (1 951) attributed great significance 

to the changes in the bone tissaeproper in resorption in addition to 

the sm-$acepherzomena on which the interest had been focused up to that 

time. They pointed out the evidence for considering the osteocyte and 



Serum Phosphorus, Calcium, and Alkaline Phosphatase 77 

the surrounding fundamental substance an entity: “If the former dies, 

the latter is destined to be resorbed. It is one of the principal laws of 

bone tissue.” RUTISHAUSER and MAJNO distinguished two types of 

osteocyte necrosis, viz., rapid necrosis and slow necrosis or oncosis. 

“Rapid necrosis apparentIy occurs in osteocytes which have been 

directly affected by traumatism, and evolves in approximately six 

hours.” The lacuna is not enlarged and presents clear-cut borders. In 

oncosis, on the other hand, the duration of the process is from 24 to 

36 hours. The osteocyte undergoes swelling, its nucleus may divide, 

and the lacuna is enlarged and appears rounded. Enlargement of the 

canaliculi causes the lacuna to be indistinctly outlined. The alkaline 

phosphatase of the bone cells varies considerably [RUTISHAUSER and 

MAJNO (1951); MAJNO and ROUILLER (1951)l. The osteoblast gives a 

highly positive alkaline phosphatase reaction. The young osteocyte 

contains the enzyme to some degree, but the adult osteocyte lacks it. 

In the osteocyte undergoing oncosis the enzyme reappears and the 

staining intensity is comparable to that of the osteoblast. No enzyme 

activity is left in the empty lacuna after oncosis. RUTISHAUSER and 

MAJNO therefore concluded that oncosis is a vital phenomenon, caused 

by irritation of the osteocyte, which then “progresses toward its 

disease and death”. They referred to this oncosis not only as a regressive 

change in the osteocyte but also as a special form of bone resorption, 

the pericytic osteo&sis. 

The studies on alkaline phosphatase of the osteoclasts by MAJNO 

and ROUILLER (1951) added further information on the role of this 

enzyme in resorption of bone. Osteoclasts in the “osteolytic phase” 

showed an intense alkaline phosphatase staining reaction and so did 

adjacent bone under resorption. In the “resting phase”, i. e., when 

osteoclasts were not actively eroding bone but were located at some 

distance from the bone surface, the osteoclasts showed almost no 

alkaline phosphatase stain reaction. MAJNO and ROUILLER then concluded 

that the alkaline phosphatase is not on4 an en? yme of bone apposition 

but also of bone resorption. 

With the results of RUTISHAUSER and his associates at hand the 

interpretation of the serum alkaline phosphatase curves and their 

inverse relation to those of the serum calcium in our NSH horses 

offers no difficulties. As the hypocalcemia progresses because of progressing 

hyperphosphatemia, the demand for calcium removal from 

the skeleton becomes greater and greater. The induced hyperparathyroidism 

causes bone resorption, and calcium is liberated to a 




greater and greater degree. Whether this initial resorption is brought 

about by some irritation of the osteocytes by the parathyroid hormone 

to cause RUTISHAUSER’S osteolysis or by stimulation of osteoclastic 

resorption is of minor importance in this connection. Regardless of 

the type of resorption, increased alkaline phosphatase levels will occur 

in blood serum. As the resorption continues, the hypocalcemia is 

gradually compensated for and the demand for calcium decreases. 

When, during the 23rd week of our experiment, hypocalcemia was 

induced once more by means of still greater phosphorus intake, the 

processes were repeated, both the decrease-increase in serum calcium 

and the increase-decrease in serum alkaline phosphatase. 

KINTNER and HOLT (1932) in single determinations in horses with 

nutritional secondary hyperparathyroidism found that serum calcium 

averaged 9% lower and serum phosphorus averaged 20% higher than 

in normal horses. GROENEWALD (1937) found no changes at all in a 

very limited number of horses. These reports emphasize the necessity 

of repeated determinations over a long period of time. It is quite 

possible to record almost normal values for serum calcium, phosphorus, 

and alkalinephosphatase evenwithsevere lesions of generalized 

osteitis fibrosa present. In our NSH horses serum phosphorus never 

returned to normal, whereas the calcium values came very close to the 

original ones after 23 weeks, just before the phosphorus intake was 

increased. 

3. Roentgenologic Changes 

The roentgenologic changes, which grew quantitatively worse, 

were qualitatively similar to those described by KINTNER and HOLT 

(1932) and GROENEWALD (1937). The changes occurred at the same 

time as clinical symptoms were apparent. This relatively late appearance 

of radiographic changes is not surprising. ALBRIGHT and 

REIFENSTEIN (1948) stated that at least 30% of the bone minerals must 

be removed to cause changes in the roentgenogram. Nevertheless, 

great importance must be ascribed to the roentgenologic examination. 

Roentgenograms showed that the changes occurred earlier in the 

mandibles than in the metacarpus. The series of roentgenograms 

further showed that the changes progressed more rapidly and were 

more severe in the mandible than in the metacarpus. This is of direct 

clinical importance. In cases of lameness, when roentgenographic 

changes of limbs suggest excessive bone resorption, the mandible 



The Parathyroid Glands 79 

should be radiographed routinely. With the method we found to be 

superior, viz., a ventrodorsal view of the rostra1 end of the mandible, a 

positive or negative diagnosis of osteitis fibrosa should offer no great 

difficulties. The resorption of the laminae durae dentes is considered 

almost specific for generalized osteitis fibrosa since it does not occur 

in rickets or osteomalacia or even in advanced cases of osteoporosis 

[ALBRIGHT and REIFENSTEIN (1 948)]. 

4. The Parathyroid Glands 

The weight increase, the morphology, and the functional evaluation 

of the parathyroid glands have conclusively shown parathyroid 

hyperplasia and cellular hypertrophy. Regarding the cell types the 

changes occurring in nutritional secondary hyperparathyroidism in the 

horse were disappearance of dark chief cells, predominance of light 

chief cells, and an increase in water-clear cells. Judging from the cytoplasm 

to nucleus ratio and the size of the nucleus of the dark and light 

chief cells, the latter indicate a more active state [EGER and VAN 

LESSEN (1954)l. The morphology of the light chief cells of NSH 

horses differed from that of the control and of the normal horses of 

Chapter I. The cells had undergone pronounced hypertrophy, the 

nucleus was significantly enlarged, and a corresponding increase in the 

cytoplasm was evidenced by an unchanged cytoplasm to nucleus ratio. 

EGER and VAN LESSEN (1954) also concluded that the small waterclear 

cells are the most active parathyroid cells and that the large 

water-clear cells represent early degeneration. CASTLEMAN and 

MALLORY (1935, 1937) stated that in primary hyperplasia of the parathyroids 

in man “a uniform direction of differentiation of all cells to 

the large water-clear cell type is the invariable finding”, whereas in 

renal secondary hyperplasia “such uniformity is lacking. Here the 

glands are composed almost completely of normal-sized chef cells, 

although a few small water-clear cells are occasionally present.” With 

regard to the functional state of the water-clear cells they wrote (1935) : 

“When the whole gland is composed of these cells, as in some cases 

of nephritis and hypertension, it is felt that hyperplasia is definite.” 

The intermediate stages during the transformation of light chief 

cells offer some information on the functional state of the end product, 

the large water-clear cell. The first thing that happens is a coalescence 




of cytoplasmic RNA. Thin flakes are formed in this manner, and as 

these are moved toward the periphery empty spaces are left in the 

cytoplasm. The process continues, and finally thck, densely packed 

RNA with intense basophlia appears to be glued to the internal 

aspect of the cell membrane. This is the reason why the water-clear 

cells are so well outlined in comparison with chief cells. Juxtanuclear 

bodies appear in the transitional stages and in the water-clear cells in 

far greater numbers than in the light chief cells. PAPPENHEIMER and 

WILENS (1935) made the same observations in water-clear cells of 

human parathyroids in renal secondary hyperparathyroidism. TRIER 

(1958), in electron micrographs, identified the juxtanuclear body as 

“stacks of parallel lamellar elements of the endoplasmic reticulum of 

the ergastoplasmic or granular type”. Such bodies appear anywhere in 

the cytoplasm and are not necessarily confined to juxtaposition. The 

transition continues : the cytoplasm becomes larger and the nucleus 

becomes pylmotic, and the stage of the large water-clear cell is thus 

reached. The empty cytoplasm does not stain with hematoxylin and 

eosin or cresylecht violet, neither is it sudanophilic. 

The cytoplasmic to nuclear ratio, the nuclear size, the staining 

properties, and the increased number of juxtanuclear bodies hardly 

support a hypothesis of hyperfunction in the water-clear cells, be it the 

small or the large ones. Instead, these characteristics point toward 

decreased function. The highest activity in the parathyroid cells under 

consideration appears to occur in the hypertrophic light chief cells. 

Both the small and large water-clear cells represent, in our opinion, 

exhausted cells. The demonstration of an unusually large number of 

water-clear cells in NSH horses would, then, indicate a longstanding 

parathyroid hyperactivity, in which these cells, after having functioned 

at greatest capacity, have become exhausted. 

YAMAGIWA et al. (1958) studied 100 cases of nutritional secondary 

hyperparathyroidism in the horse. They referred to the nests of waterclear 

cells as “pattern formation and swelling”. They stated that a certain 

relationship could often be demonstrated between this phenomenon 

and the degree of bone changes but also that severe bone lesions were 

not always associated with “pattern formation and swelling”. 

Oxyphil cells were not encountered in NSH horses or in the control. 

The significance of these cells, which do occur in the equine parathyroid, 

was discussed in Chapter I. 

The differences in the degree of hyperparathyroidism among NSH 

horses were discussed earlier (page 75). 



The Skeleton 81 

5. The Skeleton 

The histologic examination showed that the nature of the osteo- 

pathy was a generalized osteitis fibrosa. There is no need to discuss 

differential diagnosis such as osteomalacia or osteoporosis, although 

such terms still appear in the literature. 

The sites of predilection for the osseous lesions in nutritional 

secondary hyperparathyroidism in horses were shown to be the same as 

in primary (in man) or in renal secondary hyperparathyroidism (in man 

and dog). As the present work did not intend to study histologically 

the pathogenesis of the bone lesions, this aspect will not be discussed. 

Because of the balance between resorption of bone (as a tissue) on 

one hand and the apposition of osteoid and proliferation of fibrous 

tissue on the other, the volume of bones (as organs) may be decreased, 

unchanged, or increased, i. e., hypostotic, isostotic, and hyperostotic 

osteitis fibrosa, respectively. Three factors seem to be of importance in 

this respect: 

i) The degree of bone resorption; 

ii) The age of the animal; 

iii) The species. 

i) Nutritional secondary hyperparathyroidism is induced by hypocalcemia. 

The hypocalcemia is, in turn, induced by hyperphosphatemia 

due to an imbalanced calcium to phosphorus ratio in the feed. The 

greater this imbalance is, the greater the hyperphosphatemia will 

become (and therefore the subsequent changes in serum calcium, parathyroids, 

bone, and the like). If the resorption bone is thus greatly 

accelerated, the apposition of osteoid and the proliferation of fibrous 

tissue cannot keep pace with the resorption, and the volume of the 

bone decreases. If, on the other hand, the hyperparathyroidism is of 

a low grade, then the compensatory processes may predominate and 

the volume of the bones increases. Comparative pathology has shown 

this to be the case. 

Cats fed a diet consisting of minced beef heart with a calcium to 

phosphorus ratio of about 1 : 20 or beef liver with a ratio of about 

1 : 50 [WATT and MERRILL (1950)l develop secondary hyperparathyroidism 

within a short period of time. Roentgenologic evidences of 

generalized osteitis fibrosa are present within 3 weeks [KROOK et al. 

(1963)], and clinical symptoms appear within 6 to 8 weeks [SCOTT 



82 Experimental Nutritional Secondary Hyperparathyroidism in the Horse. 

Table XXII. Weight increases in some mammals 

Weight (function of birth weight) 

Birth 8 weeks of age 16 weeks of age 

Swine* 1 17 40 

Dog** 1 8 24 

Cat*** 1 7 - 

Goat** 1 3 5 

Horse, Percheron* 1 2.5 3.7 

Dairy cattle, Holstein* 1 1.7 2.8 

Beef cattle* 1 1.6 2.2 

*MUMFORD eta]., 1923; **SPECTOR, 1956; ***ALTMAN and DITTMER, 1962. 

(1957, 1959) among others]. Within 3 months the bone has almost 

disappeared. The osteitis fibrosa is of an extreme hypostotic type. 

Spontaneous cases of hyperostotic osteitis fibrosa have been described 

in the cat. In the cases described by BAUMANN (1941) and by LIEGEOIS 

(1946) the swelling of the jawbones was so severe as to interfere with 

mastication. Dietary data were not presented, but the progress of the 

disease was much slower than that in the experimental cases just 

referred to. 

ii) The importance of age is well known from spontaneous cases 

in thehorse (Chapter 111), cat,goat, swine, andmonkey [KROOK (1964)l. 

This is obviously due to the higher normal metabolic rate of bone in 

young then in old individuals. Old age does not prevent the disease, 

however [KINTNER and HOLT (1932), among others]. In renal secondary 

hyperparathyroidism the age factor is also important in the pathogenesis 

of the changes in bones. Young dogs with congenital renal 

anomalies more often develop hyperostotic osteitis fibrosa than old 

dogs with acquired chronic nephropathy [KROOK (1 964)]. 

iii) Species differences are very obvious. In the goat the great 

majority of reported cases have shown the hyperostotic type to be 

present [HINTZE (1909); ROSSWOG (1912); LESBOUYRIES and DRIEUX 

(1951); TAJIMA and OSHIMA (1951); and general descriptions by 

M6cs~ (1959), and COHRS (1961)], although the isostotic type may 

occur [CHRISTELLER (1923)l. The enlargement of the jaw is usually so 

prominent as to interfer with mastication. The swelling of the 

maxillary and nasal bones encroaches upon the upper respiratory 

passages with dyspnea as a result; hence the expressive German term 

Scbniiffeelkrankbeit (“sniffing disease”). Spontaneous nutritional second- 



The Skeleton 83 

ary hyperparathyroidism in the dog [WEBER (1929)] and in swine 

[M~CSY (1959) ; COHRS (1961)l again exemplifies hyperostotic osteitis 

fibrosa. In these two species the condition has been reproduced experimentally. 

WEBER and BECK (1932) induced J'ch;rziffehankheit in young 

dogs in 9 to 12 weeks. The dietary calcium to phosphorus ratio was not 

given; the bone lesions were hyperostotic. LIEGEOIS and DERIVAUX 

(1951) fed young pigs diets with calcium to phosphorus ratios varying 

from 1 : 5.5 to 1 : 11.6. Lameness occurred within 3 weeks, and at the 

end of the seventh week the maxillary swelling was severe enough to 

cause respiratory difficulties. Monkeys likewise are prone to develop 

hyperostotic generalized osteitis fibrosa, even with a moderately upset 

calcium to phosphorus balance in the feed [CORDY (1957); KROOIC and 

BARRETT (1962)l. In the horse the lesions develop relatively slowly and 

are usually hyperostotic (Chapter 11) but may be isostotic (this study). 

In cattle they are usually isostotic [TAMAGAWA (1956)l. 

The reasons for such species differences may be sought in differences 

in the normal growth rate (Table XXII). 

In our study clinical symptoms of general osteitis fibrosa occurred 

as early as after 12 weeks. Using a similar calcium to phosphorus 

imbalance in the diet, CRAWFORD and STURGESS (1927) recorded 

clinical symptoms only after 9 months. The explanation appears to be 

the age factor: our horses were about one-half year old at the beginning 

of the experiment; those of CRAWFORD and STURGESS were over 4 

years of age. In the experiments by NIIMI (1927) and by NIIMI and 

AOKI (1927) in which a 1 : 8.1 calcium to phosphorus ratio was used, 

the high age of the horses seems to be the explanation for the late 

occurrence of the clinical symptoms, viz., at 5 months. 

The explanation for the isostotic or slightly hyperostotic osteitis 

fibrosa in our NSH horses, in contrast to the marked hyperostotic rype 

reported in other spontaneous and experimental series appears again 

to be the age factor. A less severe calcium to phosphorus imbalance in 

the feed of young horses with a normally high metabolic rate would 

cause a more severe resorption than a more severe imbalance in adult 

horses with a relatively low metabolic rate in the skeleton. 

The clinical picture was dominated by lameness. Several authors 

[VARNELL (1 860) ; LANE (1906); ICINTNER and HOLT (1932); GREENLEE 

(1939); among others] have described joint changes which would 

explain the lameness. Because of resorption of trabeculae supporting 

the articular cartilage, this cartilage loses its support and yields to 

pressure. VARNELL also described subchondral cysts. Cartilage irregu- 

8 Krook/Lowe 



84 Expcrirncntal Nutritional Secondary 1-Iyperparalhyroidism in the I-lorse . 

larities thus occur, giving the articular surface a worm-eaten appearance. 

Such joint lesions did not occur in our experiment, and the 

morphologic background for the lameness is therefore different. As 

described above and as shown in Figs. 38 and 40, resorption of the 

outer circumferential lainella of cortical bone was an outstanding 

feature. The periosteum had thereby lost its osseous support and 

yielded to stretches from muscles and tendons attached in the area in 

question. This seems to be themost logicalexplanation for the lameness 

in our horses. In the gross description of the disease VAKNELL wrote in 

1860: "The periosteal covering of all the flat and irregular, and some 

parts of the long bones, was very vascular, and codd easib be slripped 

off" (Italics ours). 



Summary and Conclusions 

The thesis consists of two parts, viz., a description of the iiormal anatomy 

of the equine parathyroid glands and an investigation of experimental iiutritional 

secondary hyperparathyroidism iti the horse. The first part serves as a basis for the 

interpretation of the changes in the parathyroid glands in iiutritintially induced 

Iiyl'e'l.'arathyroidisin ill horses. 

Part I. The Anatomy of the Equine Parathyroid 

'l'hc material consisted of 46 horses of both sexes and of ages varyitig from 

0 to 24 years. Only horses destroyed or dead from noiiosscous and nonrenal 

disease were considered. 

'The following conclusions were drawn : 

1. 'The horse has two pairs of parathyroid glands, viz., an upper and a lower 

pair. 'l'he upper glands are located along the thyroid artery on thc antcrodorso- 

lateral aspect of the thyroid, usually not in immediate contact with it. The lowcr 

parathyroids arc located in the subcervical area on the ventral aspect of the trachca. 

'The location may vary from below the bifurcation of the hicarotid trunk to the 

upper third of the trachca. The lowcr parathyroids are about twice as large as the 

upper ones. 

2. The light chief cells predominate in the histologic picture. Water-clear 

cells occur at any age and may be fairly coninion. Dark chief cells are rclativcly 

rare, and osyphil cells are very infrequent, occurring only in old horses. Stainable 

fat may be present ill the cytoplasm of light chief cells, but it is never abuiidaiit 

and decreases with age. 'I'he nucleus of the varinus cell types is the same size as in 

man but the cytoplasm is considerably larger. 

3. 'There is no morphologic evidence for increased or decreascd parathyroid 

function with regard to sex and age. 

4. Embryonic rudiments of the parathyroid-thymus union arc of vcry 

frequent occurrence in the equine parathyroid. 'l'hey consist of epithelium on the 

external surface of the parathyroid capsule, of KURSTEINI~R'S canals and cysts at the 

hilus and within the gland, and of thymus remnants. Ectopic thyroid tissue also 

occurs within the parathyroid. Any combination of these rudiments may be found 

in one gland. 



86 Summary and Conclusions 

Part 11. Nutritional Secondary Hyperparathyroidism in the Horse 

Hyperparathyroidism was induced in three young horses by feeding them 

a diet with optimal calcium contents but with exccssive amounts of phosphorus. 

Wheat bran and sodium phosphate were used as additional phosphorus sources. 

A calcium to phosphorus ratio of 1 :3.68 was used during the first 23 weeks of the 

experiment and a ratio of 1 :6.19 during the last 18 weeks. 

The following observations and conclusions were made: 

I. Clinical Sympioms 

Insidious shifting lameness appeared from week 12 and progressed eon- 

tinuously. At the same time a "cardboard" sound occurred on percussion of the 

sinuses and it incrcased in degree likewise. Mild enlargement of the jawbones 

appeared later in the experiment. One horse suffered a distal epiphysiolysis of the 

radius. 

2. Clinico-pathologic Obseruaiion.< 

All horses responded immediately with hyperphosphatemia, the severity of 

which varied in the horses. A corresponding hypocalcemia resulted, establishing 

the inverse relationship between calcium and phosphorus in saturated blood 

serum. Hypocalcemia induced hyperparathyroidism, the biochemical evidences of 

which appeared during the 11th week. A gradual, aIthough incomplete, compensation 

for the hypocalcemia occurred during the following 12-week period. 

The changes in scrum phosphorus during this period were decrease, increase, 

decrease. The decreasing values were interpreted as expressions of increased 

renal excretion of phosphorus due to hyperparathyroidism, whereas the increase, 

which occurred simultaneously with rising serum calcium levels, occurred in 

accordance with the supersaturating factor of the parathormone as discovercd by 

&{CLEAN et al. (1946). 

At the end of this period thc phosphorus intake was increased. Once again 

the serum phosphorus increased and serum calcium decreased. After 8 weeks the 

hyperparathyroidism overcame even this excessive dietary phosphorus, and partial 

compensation for hyperphosphatemia and hypocalcemia began. The inverse relationship 

bctwcen serum calcium and phosphorus was thus showm to hold true 

in supersaturated serum. 

Serum alkaline phosphatasc was inversely related to serum calcium; with 

each decrease in serum calcium an increase in serum alkaline phosphatase occurred, 

and vice versa. In accordance with the concepts of RUTISIIAUSER and his associates 

(1951), viz., that alkaline phosphatasc is not only the enzyme of bone apposition 

but also of bone resorption, the changes in serum alkaline phosphatase were interpreted 

as indicative of the degree of bone resorption. 



Siimmary and Conclusions 87 

Rocntgcnographic changes consisted of progrcssivc radiolucency and gra- 

dually appearing coarse tralicculation and miliary mottling of bonc. ‘The appcar- 

ance of these changes coincided with the clinical symptoms. The changes occurred 

first and rcachcd the most severe degrec in the mandible. A rcntrodorsal view of 

thc rostra1 cnd of the mandible, obtaincd by placing a nonscreen film in thc mouth 

of the animal, was found to be thc method of choice. ‘The rocntgcnograms wcre 

thus of limitcd value in thc detcction of carly bonc changes in nutritional secon- 

dary hyperparathyroidism, but thc importance of roetitgcnologic cxamination 

of the niandible iii cstablishing a diagnosis of Scncralizcd ostcitis fibrosa in clinical 

cases of lamcncss bascd on csccssivc bonc resorption xvas emphasized. 

4. Necr0p.y 0b.rcrvafion.r 

’T’hc parathyroid glands cshibitcd advanccd hypcrr rophy and liylmplasia die 

degree of which was directly proportional to thc degrec of hypocalccmia. No dark 

chief cclls werc prcsent. Thc histologic picture was dominated by very hypcr- 

tropliic light cliicf cclls. The numhcr of water-clear cells was markedly incrcascd. 

Oxyphil cclls did not occur. Bccausc of the dccrcascd sizc of the nucleus, the 

incrcascd cytoplasm to nucleus ratio, the staining propcrties of the cytoplasm, aid 

the increased nuinbcr of juxtanuclear bodics in the cytoplasm, the watcr-clear cclls 

xvcre interpretcci as cshaustcd cclls. 

Thc skeleton showed generalized ostcitis fibrosa to a degree corresponding 

to the parathyroid hypcrtrophp and hyperplasia of the different horses. Sites of 

predilection of osteoclastic rcsorption were as follo\cs: cancellous bone of the 

skull; cancellous bone of thc ribs and metaphvses of long bones; uuter circum- 

fcrential lamellac of long bones ; I-lavcrsian systems of compact bone including 

compact bone coating canccllous bonc; interstitial lainellac of compact bonc. 

In thc jawbones thc changes were of a inidly hypcrostotic type, but the 

classical external appearance of “highcad” was not prcscnt. With vcry much 

accelerated resorption processes, the fibrosis and ostwid apposition, which is thc 

morphologic basis for thc swo!len facc, did not have time to dcvclop niarkedly. 

Resorption of tbc outer circ,unifcrential lamcllac of cortical bone with loss of 

osscous support for the pcriosteuni was dcsigimtcd as of spccial importance in the 

pathogcncsis of lamcncss in nutritional secondary hypcrparathyroiclisin in the 

I70rsc. 



References 

Ah~cvsi;~~, A. J. : hnatoiiiia Dotnashnich Zhivotnych (Publ. Agric. Jit., ~Iloscow 

1962). 

ALBIIIGIII~, F. and REIITNSTRIN, E.C., Jr. : Parathyroid glands and mctalxlic bone 

disease. (Williams and Wilkins, Baltimore 1948). 

ALTMAN, P. I,. and DrrMER, D. S.: Growth, including reproduction and morphological 

development. Fed. Proc. (1962). 

13Aim;ii, J

References 89 

COILIP, J. B.: 'I'hc parathyroid glands. Medzciile (13altiniorc) 5: 1 (1926). 

COPP, 1). 1H.; (;A\II,.I

90 References 

Honriz, J. and Sizmos, S.: Osteodistrokia fibrosa dos equidos. Rev. Mcd. Vet. 

(Lisboa) 39: 378 (1944). 

I IOWLAND, j. and KRAMER, B. : Calcium aiid phosphorus in the serum in relation 

to rickets. Amer. J. Dis. Child. 22: 105 (1921). 

INGLE, H. : Osteoporosis--The inineral constituents of foods. Vet. J. 16: 359 

(1909). 

~VERSEN, 1’. and LENSTRUP, E. : Forhandl. Nord. Kongr. I’aediatr. Hospitalitidende. 

62: 1079 (1919). Quoted from HARRIS, L. J.: Vitamin D and bone. In: The 

Biochemistry and Physiology of Bone, p. 581. ed. by G. BOURNE. (Academic 

Press, Ncw York 1956). 

JOEST, E. and ZUMPE, A.: Beitrag zur Icenntnis der Ostitis fibrosa des Pferdes. 

Z. Znfeekt.-Z(v. Hansiiere 27: 81 (1924). 

J~~NSSON, G. : On the etiology and pathogenesis of parturient paresis in dairy cows. 

Acta agric. scand. Suppl. 8 (1960). 

Jos~, J.: Uhcr Ostitis fibrosa bcim Pferdc. Arch. Tielbeilk. 33: 652 (1910). 

KINTNLR, J. H. and I-IOLT, R. L. : Equine ostcomalacia. Phi/&. J. Sci. 49: 1 (1932). 

Kocir, T. : Lcbrbuch dcr Vctcrinar-Anatomie, Vol. 11. (Fischer, Jena 1963). 

KRAMEK, B. and TISDALL, F.F.: A simplc technique for the dctcrniination of 

calcium and magnesium in a sinall amount of scrim. J. Did. Chcm. 47: 4.75 

(1921). 

I\ I

Refereiices 91 

~~CILAN, F. C. and URIST M.R.: Bone-An introduction to the physiology of 

skcletal tissuc, 2d cd. (Univ. Chicago Press, Chicago 1961). 

~ICLEAN, F.C.; LIPTON, MA.; BLOOM, W. and BARRON, E.S.G.: Biologic 

factors in calcification of bone. Trans. Conf. Metab. Aspccts Convalescence 

Ncw York. Jo.riak hlaTJr. Found. 14: 9 (1946). 

~'IEISSNER, W. : Uber die Epithelkiirpcrchen des Pferdes mit Bemcrliungen iibcr 

dic Nomeiiklatur der Organc. Thesis, Munich (1958). 

A~~csY, J. : Organkraiikheitai. In: Spezielle Pathologic und Therapie der I-lausticre, 

Vol. 2. (Fischer, Jcna 1959). 

AIORRISON, F. B.: Feeds and Feeding, 22nd cd. (Morrison, Ithaca, N.Y., 1956). 

MUMFORD, F. B. ct al. : Normal growth of domestic animals. Univ. Missoiiri 

Ag. Expt. .Tiat., Res. Bt://. 62 (1923). 

NATIONAL ACADEMY OF SCIENCES, WAsIImc;.roN, D. C. : Nutrient rcquirenicnts of 

horscs. Niitritional Research Comcil, Piibl. 912 (1961). 

NIIMI, I

92 References 

rcfcrciice tr) ostcogcncsis imperCccta. I'ipoc. Coqr. Bri/. .\'?/Ia// Aiiitfi. I "et. 

Au. p. 84. (L'crgamon Press, New Yorli 1959). 

Si~iic;.i OR, W. S. : Hatidhook of Biological Data. (Snundcrs, l'hiladcl~~Iiia/l~oiid~~ii 

1956). 

Sweni;, H.C. a d ~IINLS, W.H.: 'l'hc rclatii)~~ of the dietary c:a:I' ratio to serum 

(:a and parathyroid volume. J. Ni//r. 29: 43 (194.5). 

, G. \V. and CIIAWITORD, 1-1. : Ostcitis lilxosa (osteoporosis) with special 

rciicc to mineral deficieiicics in the food. Ah/. rcpf. yvt. vel sq., Ceyion 

(1927). 

~'AJIMA, Al. and OSIIIMA, I

Appendix 

Tables and Statistical Analyses 



94 Appendix 

Table I. Normal horses: Parathyroid weights and calcium, phosphorus, and alkalinc phosphatase 

values of blood serum 

Parathyroid weight Serum Ca, Serum P, Serum alkalinc 

mg/kg body weight mg/100 nil 

- - 

x s.e.m. x f s.c.111. 

mg/100 ml 

- 

x & S.C. Ill. 

phosphatase, 

sigma units 

- 

x f_ s.c.m. 

GROUP 1 1.14 & 0.20 10.95 f_ 0.32 5.77 & 0.73 5.54 f 0.64 

0-4 years (11 = 12) (11 = 6) (n = 6) (n = 5) 

Group I1 0.68 i- 0.09 11.08 f 0.45 3.33 0.62 3.67 f 0.72 

5-12 years (I1 = 12) (11 = 5) (n = 4) (n = 3) 

Group 111 0.99 0.17 10.60 f 0.25 3.53 i 0.93 4.5 

13-24 years (11 = 12) (n = 3) (n = 3) (n = 1) 

Arzn/ysi.r of vuviance of pavatlyvoid we(qhts 

Variation d.f. Mean squarcs F P 

Age groups 2 0.60 2.00 > 0.05 

Horses within age groups 33 0.30 

Y 0.88 - 0.077 X. 



Tables and Statistical Analyses 95 

7bhh ZZ. Normal horses : Parenchyma to interstitium and epithelial cytoplasm 

to nucleus ratios and epithelial nuclear surface sizes of parathyroid 

Parenchyma/ Cytoplasm/ Nuclear surface, 

interstitium 

- 

X f s.e.m. 

nucleus 

- 

x + s.e.m. 

planimeter units 

- 

x s.e.m. 

Group I 4.11 -k 0.07 4.67 & 0.05 24.75 & 0.02 

0-4 years (n - 72) (n 72) (n = 1200) 

Group I1 4.80 5 0.07 5.54 & 0.06 27.27 & 0.02 

5-12 years (n = 72) (n = 72) (n == 1200) 

Group 111 5.10 i 0.06 5.62 5 0.08 26.40 & 0.02 

13-24 years (11 = 72) (n = 72) (n = 1200) 

Analysis of variance 

Parenchyma to interstitiurn ratio 

Variation 

Age groups 

Horses within age groups 

Observations 

Cytoplasm to nucleus ratio 

Variation 

Age groups 


Observations 

Nuclear surfacc 

Variation 

Age groups 


Observations 

Linear regression epation~ 

d.f. 

2 

33 

180 

C1.f. 

2 

33 

180 

d.f. 

2 

33 

3.564 

Mean squares 

18.6693 

10.8787 

1.8660 

Plea11 squares 

20.1080 

13.9443 

0.8872 

Mean squares 

1.996 

2.792 

2.446 

F 

1.72 

5.83 

F 

1.44 

15.72 

F 

0.72 

1,141.15 

P 

>0.05 

96 Appendix 

7’uble IIZ. Experimental nutritional secondary hyperparathyroidisin in horses : 

Blood serum phosphorus, calcium, and alkaline phosphatasc 

a) Serum phosphorus (Chart 5), linear regression equations 

NSN 1 Week 0 through week 11 Y = 4.14 + 0.317 X 

Week 11 through week 12 Y = 21.40 - 1.300 X 

Week 12 through week 20 Y = 3.29 + 0.212 X 


Week 23 through week 30 Y = 4.57 +- 0.088 X 


NSH 2 

NSM 3 









Week 13 through week 16 Y : 5.02 + 0.760 X 

Weclc 16 through week 22 Y = 9.92 - 0.136 X 


Week 30 through weclr 41 Y = 11.77 - 0.125 X 

Control Week 0 through week 42 Y = 4.99 -t 0.013 X 

Mean value for control horse 5.27 & 0.06 

b) Serum calcium (Chart 6), linear regression equations 

IIorse NSII 1 Week 0 through week 10 

Week 10 through week 21 



Horse NSH 2 Week 0 through week 12 


VC’cck 22 through week 26 


Ilorsc NSI I 3 Week 1 through week 8 




Y = 11.86 - 0.160 X 

Y = 8.85 + 0.129 X 

Y = 14.42 - 0.129 X 

Y : 

8.00 t 0.077 X 

Y = 12.14 - 0.159 X 

Y 9.45 i- 0.084 X 

Y = 19.60 - 0.400 X 

Y = 8.15 1- 0.063 X 

Y = 11.89 - 0.142 X 

Y = 9.90 + 0.051 X 

Y - 13.44 - 0.121 X 

Y - 6.94 + 0.090 X 

Control horse Week 0 through week 42 Y 11.62 - 0.004 X 

Mean value for control horsc 11.53 0.06 



’Tablcs and Statistical Analyscs 97 

c) Calcium and phosphorus product (Chart 7), liiicar regression ccluntioiis 

NSH 1 

NSH 2 

NSH 3 

Control 

Week 0 through w-ccli 11 Y = 49.1 -1 2.721 X 

\Y’ccl; 11 through wcck 12 Y =z 240.0 - 15.000 X 

Wcclc 12 through week 20 Y 7 21.6 -1- 3.200 X 

Week 20 through ~ cck 29 Y xz 102.5 .- 0.999 S 

Week 29 through week 36 Y =- 36.8 - 1 - 1.143 X 

\Vcek 36 through \vcck 41 V ~- 118.7 - 1.143 X 

Week 0 through week 2 Y = 66.3 -1- 3.000 X 

Wecli 2 through wcck 12 Y = 69.2 - 0.185 X 

Week 12 through week 20 Y 7 22.9 -1 3.750 X 

Week 20 through wcck 23 Y = 258.6 - 8.200 X 

Week 23 through week 33 Y 7 38.8 -1- 0.957 X 

Week 33 through week 40 Y I= 63.6 -1- 0.190 X 

Wcclc 1 through week 6 Y = 45.3 -t 4.571 X 

Week 6 through week 13 Y -- 75.9 - 1.119 S 

Wcclc 13 through wcek 16 Y = -60.2 + 8.600 X 

Week 16 through week 26 Y 7 100.7 - 1.109 X 

Week 26 through week 34 Y 7 41.5 I- 1.117 X 

Wcclc 34 through week 41 Y = 94.8 - 0.583 X 

Week 0 through wcck 42 Y = 63.2 -1- 0.127 X 

hlcan value for control horse 60.7 .i: 0.58 

d) Serum alkaline phosphatasc (Chart 8), linc:~ regression equations 

NSIl 1 

NSH 2 

NSI-I 3 

Control 

Wc~li 0 through \\,cc~ 18 Y = 7.90 -1- 0.108 X 

W’celi 18 through wcck 27 Y : 12.29 - 0.148 S 

W’cclc 27 through wcck 31 Y :- 12.52 -1- 0.760 X 

Wccli 31 through wcck 41 Y = 22.61 - 0.385 X 

Week 0 through wcck 12 Y = 2.83 4- 0.098 X 


Wcck 21 through ucck 31 Y - 2.75 4- 0.024 X 

Week 31 through wcck 40 Y : 8.64 - 0.159 X 

Week 0 through Lvcck 16 Y 7 6.83 -1- 0.215 X 

\Week 16 through wcck 27 Y = 15.69 - 0.348 X 

Week 27 through week 31 Y ~ -5.00 -1 0.420 X 

Week 31 through week 4-1 Y -- 13.01 - 0.160 X 

Week 0 through week 42 Y =_ 8.66 -1- 0.020 X 

hlcati value for cr)iitrol horse 9.09 & 0.08 



98 Appendix 

Table ZV. Experimental nutritional secondary hyperparathyroidism in horscs : 

Parenchyma to interstitiurn and epithelial cytoplasm to nucleus ratios and nuclear 

surface sizes of parathyroid 

Horse Parenchyma/ Cytoplasm/ Nuclear surface, 

interstitium 

- 

x & s.e.m. 

nucleus 

- 

x s.e.m. 

planimeter units 

- 

x f s.e.m. 

NSH 1 

NSM 2 

NSH 3 

6.72 f 0.46 5.07 & 0.43 36.88 * 0.69 

(n = 6) (11 = 6) (n = 100) 

7.75 f 1.00 6.09 It 0.25 39.67 0.73 

(n = 6) (n = 6) (11 = 100) 

6.19 f 0.79 5.24 & 0.59 41.21 * 0.92 

(n = 6) (n = 6) (n = 100) 

Control 5.72 0.58 5.65 & 0.46 22.59 & 0.52 

(n = 6) (n = 6) (n = 100) 

Analysis of variance 

Difference from control 

Parenchyma to interstitium ratio 

Variation 

Among horscs 

Within horses 

Cytoplasm to nucleus ratio 

Variation 

Among horses 


Nuclear surface 

Variation 

Among horses 


t-analysis of nuclear surface values 

d.f. 

3 

20 

d. f. 

3 

20 

d. f. 

3 

396 

Mean squares 

4.5794 

3.2932 

Mean squares 

1.2451 

1.2229 

IMean squares 

7262.67 

53.60 

Difference from NSH 1 

F. P. 

1.39 >0.05 

F P 

1.02 >0.05 

- 

F P 

135.5

Nutritional Secondary Hyperparathyroidism in the Horse

You also want an ePaper? Increase the reach of your titles

Delete template?

Save as template?