Growth Hormone (GH)

Growth hormone, or somatotropin, is a single-chain 191-residue protein of about 22 kDa with two intramolecular disulfide bonds, produced by somatotrophs of the anterior pituitary under opposing control from hypothalamic GHRH and somatostatin. It is secreted in discrete pulses, largest during early slow-wave sleep. Its actions divide into direct effects at the growth hormone receptor, including lipolysis and the antagonism of insulin, and indirect effects mediated by IGF-1 generated mainly in the liver, including longitudinal bone growth and much of the anabolic action on tissue.

Human growth hormone was originally extracted from cadaveric pituitaries; that supply was withdrawn in 1985 after cases of Creutzfeldt-Jakob disease, and recombinant somatropin replaced it. Approved indications now span paediatric growth hormone deficiency, Turner and Prader-Willi syndromes, short stature for gestational age, chronic renal insufficiency, idiopathic short stature, adult deficiency and HIV-associated wasting, and long-acting weekly forms were approved from 2020 onward.

Two features govern how it is used. Its plasma half-life is short, fifteen to twenty minutes given intravenously, so a concentration says little and IGF-1 serves as the integrated readout of exposure. And in the United States its distribution is restricted by a drug-specific criminal statute rather than ordinary labelling rules, which is why anti-ageing and athletic supply is prosecuted differently from other off-label activity.

Two claims are worth flagging. Products sold as oral or sublingual growth hormone deliver no active hormone, since a 191-residue protein does not survive the gut intact. And growth hormone is not interchangeable with IGF-1, because the direct effects run opposite to the indirect ones, which is why growth hormone raises blood glucose while IGF-1 lowers it.