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[hyper- + parathyroid + -ism]
A condition caused by excessive levels of parathyroid hormone in the body.
SEE: hypercalcemia; SEE: parathyroid glands; SEE: osteitis fibrosa cystica

Primary hyperparathyroidism is found in about 21 people per 100,000. Most patients with hyperparathyroidism are older women.

Hyperparathyroidism is usually caused by an adenoma (benign tumor) of the parathyroid glands (primary hyperparathyroidism). Occasionally it occurs secondary to renal failure or other systemic illnesses. About 90% of the time, a single parathyroid adenoma is the cause. In about 10% of patients, generalized hyperplasia is found in all four parathyroid glands.

Hyperparathyroidism is the most common cause of hypercalcemia, which can lead to central nervous system, musculoskeletal, metabolic, gastrointestinal, and cardiovascular problems when the concentration of calcium in the blood rises to very high levels (>11 mg/dL). Common consequences of excess parathyroid hormone include symptomatic or unnoticed hypercalcemia, hypophosphatemia, hyperchlorhydria, kidney stone formation, and bone resorption.

Mild hyperparathyroidism may initially be managed expectantly without harm to the patient. Severe primary hyperparathyroidism may require surgical removal of the parathyroid gland or glands to prevent potential complications of hyperparathyroidism, including kidney stone disease, degeneration of bone, neuromuscular and neuropsychiatric illnesses, and pancreatitis. In some cancer patients, malignant tumors release a parathyroid-like hormone with hypercalcemia, which mimics hyperparathyroidism.

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