Diagnostic ultrasound ( PDFDrive )

734 PART III Small Parts, Carotid Artery, and Peripheral Vessel Sonography
population. 14 Women are afected two to three times more frequently
than men, particularly ater menopause. More than half
of patients with primary hyperparathyroidism are older than 50
years, and cases are rare in those younger than age 20.
Diagnosis
Primary hyperparathyroidism is usually suspected because an
increased serum calcium level is detected on routine biochemical
screening. Elevated ionized serum calcium level, hypophosphatasia,
and hypercalciuria may be further biochemical clues to
the disease. A serum PTH level that is “inappropriately high”
for the corresponding serum calcium level conirms the diagnosis.
Even when the PTH level is within the upper limits of the normal
range in a hypercalcemic patient, the diagnosis of primary
hyperparathyroidism should still be suspected, since hypercalcemia
from other nonparathyroid causes (including malignancy)
should suppress the glandular function and decrease the serum
PTH level. Because of earlier detection by increasingly routine
laboratory tests, the later “classic” signs of hyperparathyroidism,
such as “painful bones, renal stones, abdominal groans, and
psychic moans,” are oten not present. Many patients are diagnosed
before severe manifestations of hyperparathyroidism, such as
nephrolithiasis, osteopenia, subperiosteal resorption, and
osteitis ibrosis cystica. In general, patients rarely have obvious
symptoms unless their serum calcium level exceeds 12 mg/dL.
However, subtle nonspeciic symptoms, such as muscle weakness,
malaise, constipation, dyspepsia, polydipsia, and polyuria, may
be elicited from these otherwise asymptomatic patients by more
speciic questioning.
Pathology
Primary hyperparathyroidism is caused by a single adenoma
in 80% to 90% of cases, by multiple gland enlargement in
10% to 20%, and by carcinoma in less than 1%. 6,15,16 A solitary
adenoma may involve any one of the four glands. Multigland
enlargement most oten results from primary parathyroid
hyperplasia and less oten from multiple adenomas. Hyperplasia
usually involves all four glands asymmetrically, whereas multiple
adenomas may involve two or possibly three glands. An
adenoma and hyperplasia cannot always be reliably distinguished
histologically, and the sample may be referred to as “hypercellular
parathyroid” tissue. Because of this inconsistent pattern of
gland involvement, and because distinguishing hyperplasia from
multiple adenomas is diicult pathologically, these two entities
are oten histologically considered together as “multiple gland
disease.” 17
Causes of Primary Hyperparathyroidism
Type of Disease
Percentage
Single adenoma 80%-90%
Multiple gland disease 10%-20%
Carcinoma <1%
Most cases of primary hyperparathyroidism are sporadic.
However, prior external neck irradiation has been associated
with the development of hyperparathyroidism in a small percentage
of cases. Patients receiving long-term lithium therapy may
also present with primary hyperparathyroidism. Up to 10% of
cases may occur on a hereditary basis, most oten caused by
multiple endocrine neoplasia syndrome, type I (MEN I). his
condition is an uncommon disorder that most typically follows
an autosomal dominant pattern of inheritance and has a high
penetrance, resulting in adenomatous parathyroid hyperplasia,
as well as pancreatic islet cell tumors and pituitary adenomas.
Multiple–parathyroid gland enlargement occurs in more than
90% of patients with MEN I. 18,19 Most MEN I patients present
with hypercalcemia before their third or fourth decade of life.
Not all the parathyroid glands may be grossly enlarged at these
patients’ initial operation, but all of them likely will ultimately
be involved with hyperplasia. Patients with the MEN IIA syndrome
less frequently develop parathyroid hyperplasia. Other,
rarer familial syndromes may also be associated with primary
hyperparathyroidism caused by hyperplasia, adenomas, or
carcinoma. An important hereditary hyperparathyroidism that
must be distinguished from primary hyperparathyroidism caused
by hyperplasia or adenoma is familial hypocalciuric hypercalcemia
(benign familial hypercalcemia). Most of these patients
are asymptomatic, without the complications of primary hyperparathyroidism.
Parathyroidectomy does not cure the hypercalcemia,
and thus surgery is inappropriate.
Parathyroid carcinoma is a rare cause of primary
hyperparathyroidism. 20-23 he histologic distinction from adenoma
is diicult to establish with certainty because both carcinomas
and atypical adenomas can exhibit increased mitotic activity and
cellular atypia. Patients with parathyroid carcinoma usually present
with a very high serum calcium level (>14 mg/dL). he diagnosis
is oten made at operation when the surgeon discovers an enlarged,
irm gland that is adherent to the surrounding tissues due to
local invasion. A thick, ibrotic capsule is oten present. Treatment
consists of en bloc resection without entering the capsule, to
prevent tumor seeding. In many cases, cure may not be possible
because of the invasive and metastatic nature of the disease.
Generally, death occurs not from tumor spread but from complications
associated with unrelenting hyperparathyroidism.
Treatment
No efective deinitive medical therapies are available for the
treatment of primary hyperparathyroidism. Medications utilized
include short-term hypocalcemic agents such as calcitonin and
calcimimetics (calcium-sensing receptor agonists) such as
cinacalcet. he bisphosphonates aid in preventing bone mass
loss. Synthetic vitamin D analogs such as paricalcitol are mainly
used in the treatment of secondary hyperparathyroidism.
Surgery is the only deinitive treatment for primary hyperparathyroidism.
Studies demonstrate that surgical cure rates by
an experienced surgeon are greater than 95%, and the morbidity
and mortality rates are extremely low. 24,25 herefore in symptomatic
patients with primary hyperparathyroidism, the treatment of
choice is surgical excision of the involved parathyroid gland or
glands.