What is "parathyroid gland"

n. (context anatomy English) Any one of four endocrine glands situated in the neck, usually within a thyroid gland, which produce parathyroid hormone.

n. any one of four endocrine glands situated above or within the thyroid gland [syn: parathyroid]

The parathyroid glands are small endocrine glands in the neck of humans and other tetrapods that produce parathyroid hormone. Humans usually have four parathyroid glands, variably located on the back of the thyroid gland, although considerable variation exists. Parathyroid hormone and calcitonin (one of the hormones made by the thyroid gland) have key roles in regulating the amount of calcium in the blood and within the bones.

The parathyroid glands share a similar blood supply, venous drainage, and lymphatic drainage to the thyroid glands. The parathyroid glands are derived from the epithelial lining of the third and fourth branchial pouches, with the superior glands arising from the fourth pouch, and the inferior glands arising from the higher third pouch. The relative position of the inferior and superior glands, which are named according to their final location, changes because of the migration of embryological tissues.

Hyperparathyroidism and hypoparathyroidism, characterised by alterations in the blood calcium levels and bone metabolism, are states of surplus or insufficient parathyroid function.