Growth hormone deficiency (GHD) in adults arises as a consequence of decreased secretion of somatotropin (GH) from the anterior pituitary. The diagnosis of GHD is dependent on the demonstration of a subnormal rise in serum GH in response to one or more dynamic stimulation tests in the presence of co-existing pituitary disease or other pituitary hormone deficiencies. The syndrome of GHD is characterized by the variable presence of decreased exercise tolerance, decreased mood and decreased general well-being. These symptoms are associated with reduced bone remodelling activity, change in body fat distribution with increased central adiposity, hyperlipidaemia and increased predisposition to atherogenesis. Decreased psychological well-being and quality of life are recognised as particularly important and, from the patients' perspective, have become arguably the major indication for GH replacement therapy.The potential mitogenic effects of IGF-I have raised concerns regarding a possible increased risk of either neoplasia or regrowth of residual pituitary and peripituitary tumours. However, extensive surveillance studies have not demonstrated an increased incidence of de novo neoplasia or tumour regrowth and follow up for over 10 years on replacement show it to be effective and safe. For extensive review of all related areas of Endocrinology, visit WWW.ENDOTEXT.ORG.