Calcitonin—A new hormone from the parathyroid which lowers blood calcium

Abstract

Until recently, it was thought that the parathyroid glands secreted a single hormone (parathormone) which raised the blood calcium. A year ago, in the course of studies on the effect of various plasma calcium levels on parathyroid function, we discovered that perfusion of the isolated glands with high-calcium blood resulted in the release of a previously unsuspected hormone which actively lowered the blood calcium level. We have named this hormone “calcitonin” because it is concerned with maintaining the normal level or “tone” of calcium in body fluids. It is fast and short-acting, the maximum fall in plasma calcium occurring within 20 to 30 minutes following a single injection, after which the level returns to normal within an hour. There is accumulating evidence that the parathyroid glands play an active role in controlling hypercalcemia. If the parathyroid glands are removed after infusion of parathyroid extract, or after EDTA-induced hypocalcemia which stimulates endogenous parathormone production, there is a prompt rise in plasma calcium which does not occur if the glands are left intact. A rise in plasma calcium also occurs if parathyroidectomy is performed during calcium infusion.