EQUINE CLINICAL PATHOLOGY - Rossdale & Partners

More documents

Recommendations

Info

T h e B e a u f o r t c o t t a g e l a b o r a t o r i e s Oestrone sulphate rig test Normal male Cryptorchid ‘False rig’ Oestrone sulphate 10-50 ng/ml 0.1-10 ng/ml 0-0.02 ng/ml hCG/testosterone rig test Testosterone stimulation test should be used for all donkeys and in horses under 3 years old. Testosterone levels are measured in serum (clotted) or heparinised plasma samples taken before and then 30-120 minutes after the intravenous injection of 6000 iu hCG. Normal male Cryptorchid ‘False rig’ Testosterone (1) 5-30 nmol/l 0.3-4.3 nmol/l 0.03-0.15 nmol/l Testosterone (2) 5-30 nmol/l 1.0-12.9 nmol/l 0.05-0.19 nmol/l and suggest that prostaglandin treatment should induce luteolysis, providing that the corpus luteum is more than 4 days old. In the pregnant mare, there is no proven relationship between progesterone levels and the integrity of pregnancy. Mares with levels 4 ng/ml but there is considerable daily and individual variation. The progesterone assay is in no way an accurate pregnancy test but may be helpful, or reassuring to managers, in monitoring individual mares with histories of repeated pregnancy failure. Granulosa Cell Tumour (GCT) The most common ovarian tumour in the mare is the granulosa cell tumour (GCT). GCT’s produce steroid hormones which can be detected in elevated quantities in the peripheral blood. In cases where the tumour has a significant theca cell component (approximately 54% of cases), serum testosterone is elevated. These mares are more likely to be aggressive and stallion like. GCT mares showing anoestrus or persistent oestrus may have normal testosterone concentrations. Inhibin concentrations have been found to be elevated above normal in approximately 87% of mares with GCT’s, and therefore inhibin appears to be a more accurate indicator of the presence of a GCT than testosterone alone. We recommend measurement of serum testosterone and inhibin to support an ultrasonographic diagnosis of GCT, or in cases in which rectal palpation is undesirable. 34
G u i d e t o e q u i n e c l i n i c a l p a t h o l o g y Cryptorchidism Oestrone sulphate assay may be used as a cryptorchid or 'rig' test for horses (not for donkeys) that are over 3 years old (see table on left). Thyroid function Thyroid hormones, i.e. thyroxine (T4) and tri-iodothyronine (T3) are measured in equine serum samples. As diurnal rhythms are involved, two samples should be collected ideally early in the morning and late in the afternoon. Low levels (T4 240 nmol/l) in classical cases (aged, hirsute, polydipsic, polyuric, glucosuric). However, basal levels are often within normal range for younger, developing cases and so TRH stimulation test, overnight dexamethasone suppression test or combinations of such tests are needed to help define pituitary normality or abnormality. Insulin Serum insulin is sometimes a useful ‘screening’ test for equine Cushing’s syndrome. Results 1000 miu/ml. Overnight dexamethasone suppression test This test is based upon the fact that dexamethasone administration suppresses plasma cortisol in normal horses because of feedback on ACTH release. A resting serum sample is collected at 5 pm and 40 µg/kg DXM (Azium, Gist-Brocades, 20 mg/500 kg horse) is injected im. A follow-up serum sample is collected at 12 pm the following day. Normal horses show a suppression of serum cortisol levels to
Page 1 and 2: the beaufort cottage laboratories G
Page 3 and 4: G u i d e t o e q u i n e c l i n i
Page 33: G u i d e t o e q u i n e c l i n i

EQUINE CLINICAL PATHOLOGY - Rossdale & Partners

You also want an ePaper? Increase the reach of your titles

Delete template?

Save as template?