Changes in body composition and leptin levels during growth hormone (GH) treatment in short children with various GH secretory capacities

Objective: The aim of this study was to follow changes in body composition, estimated by dual-energy X-ray absorptiometry (DXA), in relation to change s in leptin during the first year of GH therapy in order to test the hypoth esis that leptin is a metabolic signal involved in the regulation of GH sec retion in children, Design and Methods: In total, 33 prepubertal children were investigated. Th eir mean (S.D.) chronological age at the start of GH treatment was 11.5 (1. 6) years, and their mean height was - 2.33 (0.38) S.D. scores (SDS). GH was administered subcutaneously at a daily dose of 0.1 (n = 26) or 0.2 (n = 7) IU/kg body weight. Ten children were in the Swedish National Registry for children with GH deficiency, and twenty-three children were involved in tri als of GH treatment for idiopathic short stature. Spontaneous 24-h GH secre tion was studied in 32 of the children. In the 24-h GH profiles, the maximu m level of GH was determined and the secretion rate estimated by deconvolut ion analysis (GH,). Serum leptin levels were measured at the start of GH tr eatment and after 10 and 30 days and 3, 6 and 12 months of treatment. Body composition measurements, by DXA, were performed at baseline and 12 months after the onset of GH treatment. Results: After 12 months of GH treatment, mean height increased from - 2.33 to - 1.73 SDS and total body fat decreased significantly by 3.0 (3.3)%. Se rum leptin levels were decreased significantly at all time points studied c ompared with baseline. There was a significant correlation between the chan ge in total body fat and the change in serum leptin levels during the 12 mo nths of GH treatment, whereas the leptin concentration per unit fat mass di d not change, In a multiple stepwise linear regression analysis with 12 mon th change in leptin levels as the dependent variable, the percentage change in fat over 12 months. the baseline fat mass (%) of body mass and GH, acco unted for 24.0%, 11.5% and 12.2% of the variability respectively. Conclusions: There are significant correlations between changes in leptin a nd fat and endogenous GH secretion in short children with various GH secret ory capacities. Leptin may be the messenger by which the adipose tissue aff ects hypothalamic regulation of GH secretion.