Definition:

Hypoparathyroidism is characterized by hypocalcemia and hyperphosphatemia resulting from insufficient or defective parathyroid hormone (PTH) action. PTH is a key calcium regulating hormone essential for calcium homeostasis, vitamin D-dependant calcium absorption, renal calcium reabsorption and renal phosphate clearance. Hypocalcemic patients can present with a wide range of symptoms, including fatigue, cramping, tetany, seizures and congestive heart failure. Mild chronic hypocalcemia can be asymptomatic. The most common cause of hypoparathyroidism is iatrogenic in the setting of anterior neck surgery. Hypoparathyroidism may be due to congenital or acquired disorders. Causes include autoimmune diseases, genetic abnormalities, destruction or infiltrative disorders of the parathyroids. Hypoparathyroidism may be further classified as isolated or syndromic. Genetic syndromes with hypoparathyroidism include DiGeorge syndrome (H01524), HDR syndrome (H01271), Kenny-Caffey syndrome (H00619), Kearns-Sayre syndrome (H01355), and so on. Isolated hypoparathyroidism has been reported as apparently sporadic, or as a familial trait with either autosomal dominant, autosomal recessive, or X chromosome-linked inheritance. Mutations in the preproPTH gene have been described in both autosomal dominant and autosomal recessive forms of familial isolated hypoparathyroidism. And a mutation of the parathyroid-specific transcription factor GCMB (GCM2) gene has also been reported in autosomal recessive hypoparathyroidism. Oral calcium and vitamin D analogs are critical in the treatment of hypocalcemia.