Parathyroid Hormone (PTH)

Parathyroid hormone is secreted by the parathyroid glands as a polypeptide containing 84 amino acids. It acts to increase the concentration of calcium (Ca²⁺) in the blood, whereas calcitonin (a hormone produced by the parafollicular cells (C cells) of the thyroid gland) acts to decrease calcium concentration. PTH acts to increase the concentration of calcium in the blood by acting upon parathyroid hormone receptor in three parts of the body: PTH half-life is approximately 4 minutes. It has a molecular mass of 9.4 kDa.

PTH was one of the first hormones to be shown to use the G-protein, adenylyl cyclase second messenger system.Normal total plasma calcium level ranges from 8.5 to 10.2 mg/dL (2.12 mmol/L to 2.55 mmol/L).