Physiology, Parathyroid Hormone

Abstract

In the blood, the sensitive process of calcium and phosphate homeostasis is maintained primarily by an appropriately functioning parathyroid gland. The parathyroid gland is comprised of 4 small glands located posteriorly to the thyroid in the middle aspect of the anterior neck. The parathyroid gland secretes parathyroid hormone (PTH), a polypeptide, in response to low calcium levels detected in the blood. PTH facilitates the synthesis of active vitamin D, calcitriol (1,25-dihydroxycholecalciferol, or vitamin D3) in the kidneys. In conjunction with calcitriol, PTH regulates calcium and phosphate. PTH effects are present in the bones, kidneys, and small intestines. As serum calcium levels drop, the secretion of PTH by the parathyroid gland increases. Increased calcium levels in the serum serve as a negative-feedback loop signaling the parathyroid glands to stop the release of PTH. The mechanism of PTH in the body is intricate, and the clinical ramifications of irregularities are significant. The understanding of PTH is of paramount relevance and importance.