Abstract
Despite early evidence from studies performed soon after its discovery, the role of human growth hormone (GH) in metabolic processes during adulthood has, until recently, been largely ignored. The importance of GH in the regulation of body composition in the adult is clearly demonstrated by the abnormalities seen in "nature's experiments', i.e. acromegaly and GH deficiency. Body composition has been shown to change favourably following successful treatment of acromegaly. Formal replacement studies in adult GH-deficient patients, made possible by the recent advent of recombinant GH, have also shown dramatic changes in body composition, with increases in lean body mass and reductions in fat mass towards normality and associated improvements in physical performance. Thus, adult GH deficiency, like acromegaly, has become widely accepted as a distinct clinical entity warranting treatment.