Parathyroid gland

Parathyroid gland, any of 4 small endocrine bodies behind the thyroid that regulate calcium and phosphorus metabolism. Parathyroid hormone, produced when the concentration of calcium ions in the blood is low, takes calcium from the bone and increases absorption of calcium in the intestines and kidneys. The hormone also decreases the phosphate ion concentration. An imbalance in parathormone levels leads to calcium deficiency (low levels) or bone degeneration (high levels).

See also: Gland.