Causes and Risks

Calcium and phosphorus are important body minerals. They form the mineral component of bones, and they exist as charged particles called ions in the blood and inside cells.

A hormone called parathyroid hormone (PTH) regulates the amount of calcium and phosphorus in bone and blood. Four small glands called parathyroid glands make PTH. The parathyroid glands are located behind the thyroid gland in the neck.

Hypoparathyroidism is the clinical condition caused by a lack of parathyroid hormone. Calcium levels in the blood fall, and phosphorus levels rise. Low blood calcium levels may cause symptoms such as tingling of the lips, fingers and toes, and muscle cramps, or spasms.

The most common cause of hypoparathyroidism is injury to the parathyroid glands during head and neck surgery.

Rarely, hypoparathyroidism is a side effect of radioactive iodine treatment for hyperthyroidism. PTH secretion may be impaired when blood levels of the element magnesium are low or when blood pH is too high, a condition called metabolic alkalosis.

DiGeorge syndrome is a childhood disease in which hypoparathyroidism occurs due to congenital absence of the parathyroid glands. Familial hypoparathyroidism occurs with other endocrine diseases such as adrenal insufficiency in a syndrome called Type I polyglandular autoimmune syndrome (PGA I).

Risk factors for hypoparathyroidism include recent thyroid or neck surgery, family history of parathyroid disorder, or history of certain autoimmune endocrine diseases such as Addison's disease. The incidence is about 4 out of 100,000 people.

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