In the 1980s, many endocrinologists were still sceptical that growth hormone (GH) played an active role in adult metabolism. This is, perhaps, surprising given that GH deficiency (GHD) in adulthood had been recognized as long ago as the 1960s. Studies have shown that GHD in adulthood is a far-reaching syndrome associated with abnormal body composition, reduced bone mineral density with an increased fracture rate, increased cardiovascular morbidity and impaired cardiac function, as well as reduced exercise performance and decreased psychological well-being. Importantly, it is also clear, from placebo-controlled trials, that GH replacement therapy can normalize body composition, increase bone mineral content and improve the cardiovascular risk factor profile. GH replacement therapy also improves cardiac performance and exercise capacity, increases muscle strength and improves well-being and quality of life.