Several reports have focused on the clinical features of the untreated GH-deficient adult and the effect of GH therapy. The results reported are strikingly unanimous. Untreated GH-deficient adults have been shown to have increased cardiovascular mortality, reduced exercise capacity, reduced muscle strength, subnormal glomerular filtration rate and renal plasma flow, defective sweat secretion and defective thermoregulation, reduced energy expenditure and basal metabolic rate, abnormal thyroid hormone metabolism, reduced myocardial function and clinical signs of premature atherosclerosis. Body composition has been found abnormal with increased fat mass, decreased lean body mass, decreased muscle fat ratio, visceral obesity, reduced extracellular fluid volume and reduced bone mineral content. Furthermore, two independent groups have reported impaired psychological wellbeing as compared to normal subjects. Apart from the observation on total mortality, all the above-reported abnormalities improve during GH substitution. The only recognisable side effect so far has been fluid retention, which is usually transient and dose-dependent. It is concluded that GH deficiency has distinct clinical consequences all of which can be totally or partially alleviated by GH replacement therapy.