Alterations in body composition and fat distribution in growth hormone-deficient prepubertal children during growth hormone therapy

Growth hormone (GH) deficiency in children results in increased body fat, r educed fat-free mass (FFM) including muscle (protein) and bone, and abdomin al obesity. Thus, proper GH secretion likely has major developmental influe nces on later health risks including cardiovascular diseases and osteoporos is. However, the in vivo control of the development of the body composition and fat distribution by GH has not yet been accurately investigated using children with GH deficiency as a model. Wa determined the effect of GH ther apy (GH replacement, n = 3; GH + physiologic cortisol and thyroxine replace ment, n = 3) on body composition, the proportional composition of the FFM, and body fat distribution in GH-deficient prepubertal children compared wit h healthy control children (n = 6) not treated with GH. The GH-deficient an d control children were initially matched for gender, bone age, and weight. As assessed by a 4-compartment model, GH therapy reduced percent body fat during the first 3 months of therapy but not thereafter. This change was pr imarily due to FFM, which increased 3-fold more in the GH-deficient group a nd accounted for 91.5% of the increase in body weight. Fat mass increased i n the controls but was unchanged in the GH-deficient group. Therapy tempora rily increased the proportional contribution of water to the FFM, decreased the proportion of mineral, and slightly increased the proportion of protei n. Using magnetic resonance imaging (MRI), abdominal visceral fat was reduc ed in the GH-deficient group and unchanged in the controls. Abdominal subcu taneous fat measured in the same image was not changed. The abdominal and s uprailiac skinfold thicknesses also were not decreased in the GH-deficient group. In conclusion, within 1 to 3 months, GH therapy accelerates lean tis sue accrual, especially the water and protein components, but has a smaller effect on reducing fat mass. GH therapy has site-specific effects on reduc ing abdominal adiposity. Copyright (C) 2001 by W.B. Saunders Company.