Secreted by the parathyroid gland, Parathyroid Hormone (PTH) contains 84 amino acids as a polypeptide and essentially works to increase the concentration of calcium in the body by acting on receptors present in the bones and kidney, as well as receptors in the central nervous system, pancreas, testis, and placenta.
Intact PTH is biologically active and circulates with a half-life of approximately four minutes. Measurement of intact PTH provides the most specific way to diagnosis primary hyperparathyroidism as it can differentiate from other (non-parathyroid-mediated) forms of hypercalcemia, such as malignancy, sarcoidosis, and thyrotoxicosis.