Hypoparthyroidism is a deficiency of parathyroid hormone that causes abnormal metabolism of calcium and phosphorus.

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.

Parathyroid hormone (PTH) regulates the amount of calcium and phosphorus in bone and blood. The four small parathyroid glands located in the neck, behind the thyroid, make PTH.

Hypoparathyroidism is the clinical condition caused by a lack of PTH. Blood calcium levels 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 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.