Growth Hormone (GH)
A 191 amino acid protein hormone secreted by the anterior pituitary gland that stimulates growth, cell reproduction, and tissue regeneration. Growth hormone acts both directly and through IGF-1. Somatropin is the recombinant form used therapeutically for GH deficiency.
Technical Context
GH is released in pulsatile bursts from anterior pituitary somatotrophs, primarily during deep sleep (stages 3-4). Release is stimulated by GHRH and ghrelin, and inhibited by somatostatin and IGF-1 (negative feedback). GH acts directly on tissues (lipolysis, glucose counterregulation) and indirectly through hepatic IGF-1 production (growth, anabolic effects). GH deficiency in children causes growth failure; in adults it produces decreased bone density, increased visceral fat, reduced lean mass, and impaired quality of life. Recombinant somatropin (identical to 22 kDa human GH) requires daily injection; next-generation long-acting GH products include somapacitan (weekly, albumin-binding) and somatrogon (weekly, using CTP fusion technology).