Growth hormone

Growth hormone (GH, somatotropin) is a 191-amino-acid single-chain polypeptide secreted by somatotroph cells of the anterior pituitary. It acts on virtually all body tissues, directly via the growth hormone receptor and indirectly through the hepatic production of insulin-like growth factor 1 (IGF-1). GH is essential for linear growth in children and plays continuing roles in adult metabolism, body composition, and tissue repair.

Pulsatile secretion

Endogenous GH is released in pulses, with the largest pulse occurring during the first hours of slow-wave sleep. Pulse amplitude is governed by hypothalamic growth hormone-releasing hormone (GHRH) and inhibited by somatostatin. Ghrelin and synthetic growth hormone secretagogues act on a separate receptor (GHSR-1a) to stimulate release.

Therapeutic and non-medical use

Recombinant human GH (rhGH) is FDA-approved for pediatric growth-hormone deficiency, adult GH deficiency, Turner syndrome, and several other indications. Non-medical use for muscle gain, fat loss, and “anti-aging” is widespread and is prohibited under WADA section S2.

Distinction from GH-axis peptides

The peptides catalogued on Retapedia under the growth hormone tag do not contain GH itself. They either signal the pituitary to release more endogenous GH (GHRH analogues, secretagogues) or supply downstream effectors such as IGF-1 LR3.