GH is a member of the large family of growth factors that includes prolactin, placental lactogens, proliferins, and somatolactin. Additionally, GH is a 191-amino acid, single-chain polypeptide that is synthesized, stored, and secreted by somatotropic cells within the lateral wings of the anterior pituitary gland. Release of GH into the circulation is mediated by the concerted actions of the hypothalamic hormones-GH-releasing hormone (GHRH) and somatostatin (SST), as well as through signals from the periphery-ghrelin and leptin.
