Hypoparathyroidism occurs when your parathyroid glands don't secrete enough parathyroid hormone. You have four parathyroid glands — each normally about the size of a grain of rice — situated in your neck, adjacent to your thyroid gland.

The low production of parathyroid hormone leads to abnormally reduced calcium levels (hypocalcemia) in your blood and bones and to increased levels of phosphorus (hyperphosphatemia).

Factors that can cause hypoparathyroidism include:

  • Acquired hypoparathyroidism. This most common cause of hypoparathyroidism develops after accidental damage to or removal of the parathyroid glands during surgery. This surgery may be a treatment for diseases of the nearby thyroid gland, or for throat cancer or neck cancer. Today, surgeons are aware of and more careful to avoid injuring the parathyroid glands during surgery.
  • Hereditary hypoparathyroidism. In this form, either the parathyroid glands aren't present at birth, or they don't work properly. Some types of hereditary hypoparathyroidism are associated with deficiencies of other hormone-producing glands.
  • Autoimmune disease. In this condition, your immune system creates antibodies against the parathyroid tissues, trying to reject them as if they were foreign bodies. In the process, the parathyroid glands stop manufacturing their hormone.
  • Extensive cancer radiation treatment of your face or neck, which can result in destruction of your parathyroid glands, or occasionally because of radioactive iodine treatment for hyperthyroidism.
  • Low levels of magnesium in your blood, which can affect the function of your parathyroid glands. Normal magnesium levels are required for optimum secretion of parathyroid hormone.
Oct. 24, 2012