Chromogranin A: a novel regulator of parathyroid gland secretion.

Chromogranin A (CgA) is a major protein of the parathyroid gland that is costored and cosecreted with parathyroid hormone (PTH). CgA, widely distributed in endocrine and neuroendocrine cells in addition to parathyroid cells, appears to be a precursor of biologically active autocrine or paracrine peptides that include pancreastatin (CgA240-288) and parastatatin (CgA347-419), compounds that strongly inhibit stimulated secretion of PTH and costored CgA. The biosynthesis of CgA and PTH via gene expression and mRNA translation are noncoordinately altered by agents that affect parathyroid cell secretion including 1,25 dihydroxycholecalciferol, dexamethasone and Ca2+. These data have been interpreted to support an important physiological role for CgA-derived peptides as autocrine, paracrine and endocrine agents in the regulation of parathyroid cell function and secretion.