GH/IGF-I regulation in obesity--mechanisms and practical consequences in children and adults.

Growth hormone (GH) secretion in children and adults is profoundly, but reversibly, suppressed in obesity. Since GH deficiency leads to increased fat mass, differentiation of both conditions remains challenging. Here we review the known and still speculative mechanisms underlying the inhibitory effects of obesity on GH secretion including peripheral factors like IGF-I and insulin, as well as central hypothalamic/pituitary modulators. We further discuss the basis of current testing for GH deficiency in obesity and the validity of the various provocative tests in overweight subjects.