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PRIMARY HYPERPARATHYROIDISM
(I HPTH)
Definition
Primary, or first degree, or hypercalcemic hyperparathyroidism is
an intrinsic dysfunction of the parathyroid gland which causes increased
production of the parathyroid hormone and hypercalcemia.
Epidemiology
It is a relatively common disease that occurs in 1 of every 500
women, and in 1 of every 2000 men over the age of forty years (3).
The most common causes of I HPTH in decreasing order of occurrence
are: parathyroid adenoma, multiglandular hyperplasia (of primary
or secondary nature), multiple adenomas (double or triple), and
rarely carcinoma and ectopic adenomas.
I HPTH is suspected whenever certain laboratory
findings or clinical signs or symptoms are present. Diagnosis can
be further confirmed by special imaging techniques
Laboratory findings
Increased serum parathyroid hormone (PTH) concentration
is largely responsible for the most common biochemical manifestations
of parathyroid adenoma which include hypercalcemia, hypophosphatemia
and elevated serum chloride. There may be an increase in bone remodeling
markers such as serum alkaline phosphatase, osteocalcin (increased
bone formation marker), and hydroxyproline (bone resorption marker).
Here it is worth mentioning that ectopic production of PTH can give
a false positive diagnosis of parathyroid adenoma but this is quite
rare( 4,5).
Clinical manifestations
The clinical manifestations of I HPTH encompass
bony changes, renal complications, gastrointestinal(GI) symptoms
and possible neurological deterioration.
Bone demineralization symptoms "may range
from a syndrome of vague diffuse bone pain or arthralgias, to a
severe deforming bone disease (osteitis fibrosa cystica)".
A generalized concomittent increase in both osteoclastic bone resorption
and osteoblastic
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activity accompanied by a fibrovascular marrow replacement is the
underlying pathogenetic mechanism of this clinically prominent feature.
Cortical bone erosion and demineralization correlate well with bone
pain, shoulder bowing, kyphosis, height loss and collapse of lateral
ribs ("pigeon breast").
Renal complications occur in 10% of primary hyperparathyroid
patients, most probably those with a preexisting additional risk
factor for calcium stone formation, and include recurrent calcium
nephrolithiasis, nephrocalcinosis and functional abnormalities that
could possibly lead to end-stage renal failure. These changes manifest
themselves as recurrent flank pain, polyuria, and polydipsia.
Occasional GI complications may occur such as
peptic ulcer disease, partly attributable to the increased serum
gastrin values ensuing from the hypercalcemia per se, and recurrent
or severe pancreatitis the mechanism of which is still poorly understood.
Neuropsychiatric symptoms are more likely to
occur in elderly patients, and range from weakness, fatigue, apathy,
or difficulty in concentration, to dementia, psychosis or coma.
Neurogenic muscle atrophy with proximal muscular weakness, and possibly
gout and pseudogout may also occur (4,5).
Imaging techniques
X-Rays. Specific radiologic features of bone
dimeniralization may show on X-ray studies of the skeletal system.
Characteristic subperiosteal resorption, mostly in the phalanges
of the hand, bone cysts, usually multiple and in the central medullary
portions of the shafts of the metacarpals, ribs or pelvis, osteoclomas
or "brown tumors", mostly in the trabecular portions of
the jaw, long bones, and ribs, and pathologic fractures are among
the radiologic findings consistent with the bone involvement in
I HPTH (4,5). But "imaging hyperparathyroidism has lately shifted
from the detection of skeletal manifestations to localizing the
source of abnormal hormone production" especially with the
advent of new imaging modalities such sonography (U/S), computed
tomography (CT), magnetic resonance imaging (MRI) and Tc-99m Sestamibi
scintigraphy.
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