GROWTH-HORMONE DEFICIENCY IN ADULTS

After the cessation of longitudinal growth, growth hormone (GH) contin ues to subserve an important role in the regulation of body metabolism to optimize body composition and function, Adults who are deficient i n GH exhibit a number of abnormal features including increased adiposi ty and reduced lean body mass associated with reduced physical fitness . These features are reversible with GH therapy and suggest the need f or long term GH replacement in GH-deficient adults. Accurate diagnosis of GH deficiency is important because GH replacement is an expensive, life-long treatment, Although GH deficiency causes recognizable physi cal changes, the clinical features are not sufficiently distinct to pe rmit accurate bedside diagnosis. GH status is traditionally assessed b y undertaking stimulation tests, by measuring spontaneous secretion, o r by measuring markers of GH action such as insulin-like growth factor -1 (IGF-1) and IGF binding protein-1 (IGFBP-3). In an evaluation of th e relative merits of these three diagnostic testing modalities (specif ically the insulin tolerance test [ITT], mean 24 hour GH levels, IGF-1 , and IGFBP-3), the ITT was found to be the most accurate test, The IT T correctly identified all patients with GH deficiency with a GH respo nse clearly below that of healthy subjects. The use of other stimulati on tests should not be extrapolated from the ITT and needs to be indep endently evaluated.