parathyroid hormone n a hormone of the parathyroid gland that regulates the metabolism of calcium and phosphorus in the body abbr. PTH called also parathormone
* * *
a hormone, synthesized and released by the parathyroid glands, that controls the distribution of calcium and phosphate in the body. A high level of the hormone causes transfer of calcium from the bones to the blood; a deficiency lowers blood calcium levels, causing tetany. This condition may be treated by injections of calcium gluconate. Compare calcitonin.
* * *
a polypeptide hormone (84 amino acid residues) secreted by the parathyroid glands. It promotes release of calcium from bone to extracellular fluid by activating osteoclasts and inhibiting osteoblasts, indirectly promotes increased intestinal absorption of calcium, promotes renal tubular reabsorption of calcium and increased renal excretion of phosphates, and is a major regulator of bone metabolism. Secretion of parathyroid hormone increases when the level of calcium in the extracellular fluid is low. Its action is opposed by that of calcitonin. Called also parathormone and parathyrin.Medical dictionary. 2011.