PARATHYROID GLANDS
Primary hyperparathyroidism can be caused by the
following:
•
Adenomas (80%); may be associated with MEN 1
•
Parathyroid hyperplasia (15%)
°°
Characterized by diffuse enlargement of all 4 glands; the enlarged
glands are usually composed of chief cells
°°
Parathyroid carcinoma is very rare
•
Hyperparathyroidism can also occur as a paraneoplastic syndrome of
lung and renal cell carcinomas.
The excess production of
parathyroid hormone (PTH) leads to hypercalcemia, with lab studies showing
elevated serum calcium and PTH.
Primary hyperparathyroidism is often asymptomatic, but
may cause kidney stones, osteoporosis and osteitis
fibrosa cystica, metastatic calcifications, or neurologic changes.
Secondary hyperparathyroidism is caused by any disease that
results in hypocalce-mia, leading to increased secretion of PTH by the
parathyroid glands; it can result from chronic renal failure, vitamin D
deficiency, or malabsorption.
Hypoparathyroidism can result from the surgical
removal of glands during thy-roidectomy, DiGeorge syndrome, or a hereditary
autoimmune syndrome caused by mutations in the autoimmune regulator gene AIRE. Patients present with muscle spasm
and tingling of toes and lips. The hypocalcemia may also cause psychiatric
disturbances and cardiac conduction defects (ECG: prolonged QT interval).
Treatment of
hypoparathyroidism is vitamin D and calcium.
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