Parathyroid hormone (PTH) is secreted by the chief cells of the parathyroid glands as a polypeptide containing 84 amino acids with molecular weight of 9.4KDa.

PTH acts to increase the concentration of calcium (Ca2+) in the blood by acting upon parathyroid hormone receptor in three parts of the body: bone, kidney and intestine. In addition to regulation of serum calcium levels, PTH also plays role in regulating serum phosphate and vitamin D synthesis. PTH reduces the reabsorption of phosphate from the proximal tubule of the kidney, resulting in increased phosphate excretion through the urine. However, PTH enhances the uptake of phosphate from the intestine and bones into the blood. In the bone, slightly more calcium than phosphate is released from the breakdown of bone. In the intestines, which are mediated by an increase in activated vitamin D, the absorption of phosphate is not as dependent on vitamin D as is that of calcium. The end result is a small net drop in the serum concentration of phosphate. PTH increases the activity of 1-alpha-hydroxylase enzyme, which converts 25-hydroxycholecalciferol to 1,25-dihydroxycholecalciferol, the active form of vitamin D.

PTH has shown significant clinical applications. A high level of PTH in the blood is known as hyperparathyroidism. The causes of primary hyperparathyroidism are parathyroid adenoma, parathyroid hyperplasia and parathyroid cancer. The cause for secondary hyperparathyroidism is often due to in chronic renal failure.

Standard, Biotinylated Parathyroid Hormone (PTH) peptide, and Positive Control should be stored at -20°C after arrival. Avoid multiple freeze-thaws. The remaining kit components may be stored at 4°C. Opened Microplate Wells and antibody (Item N) may be stored for up to 1 month at 2° to 8°C. Return unused wells to the pouch containing desiccant pack and reseal along entire edge.