Growth hormone deficiency in adults

After the cessation of longitudinal growth, growth hormone (GH) continues to subserve an important role in the regulation of body metabolism to optimize body composition and function, Adults who are deficient in GH exhibit a number of abnormal features including increased adiposity and reduced lean body mass associated with reduced physical fitness. These features are reversible with GH therapy and suggest the need for 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 physical changes, the clinical features are not sufficiently distinct to permit accurate bedside diagnosis. GH status is traditionally assessed by undertaking stimulation tests, by measuring spontaneous secretion, or 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 the relative merits of these three diagnostic testing modalities (specifically 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 ITT correctly identified all patients with GH deficiency with a GH response clearly below that of healthy subjects. The use of other stimulation tests should not be extrapolated from the ITT and needs to be independently evaluated.