Parathyroid Hormone (58004P) (58004P-500ug)

Parathyroid hormone (PTH) is a 84-amino acid polypeptide secreted by parathyroid glands that increases the concentration of calcium in the blood through its interaction with parathyroid hormone receptors in bones, kidney, and intestines. In bones PTH enhances the release of calcium from the large reservoir contained in bones, in kidney it enhances active reabsorption of calcium from distal tubules and the thick ascending limb, and in intestines it enhances the absorption of calcium by increasing the production of vitamin D and upregulating the enzyme responsible for 1-alpha hydroxylation of 25-hydroxy vitamin D, converting vitamin D to its active form (1,25-dihydroxy vitamin D) which effects the absorption of calcium (as Ca2+ ions) by the intestine via calbindin.