The parathyroid glands
The parathyroid glands are two small oval-shaped glands located adjacent to the two thyroid gland lobes in the neck.
Parathyroid glands produce parathyroid hormone, which plays a role in regulating calcium levels in the blood. Precise calcium levels are important in the human body; small deviations can cause muscle and nerve impairment.
Besides regulating the release of calcium from bones into the bloodstream, parathyroid hormone stimulates food absorption by the intestines and calcium conservation by the kidneys.
Hypoparathyroidism is caused by underactive parathyroid glands. The poor production of parathyroid hormone causes, in turn, low levels of calcium in the bloodstream. This leads to tetany, or an increased excitability of the nerves. Causes of hypoparathyroidism include accidental removal of a parathyroid gland or part of the parathyroid tissue during thyroid removal surgery.
Parathyroid tumors, on the other hand, may cause increased parathyroid hormone levels, leading to hyperparathyroidism. Cancers of the parathyroid are very rare; most parathyroid tumors are benign (noncancerous) adenomas and can be surgically removed.