Leptin concentrations in Prader-Willi syndrome before and after growth hormone replacement

OBJECTIVE This study explored leptin concentrations in Prader-Willi syndrom e (PWS), a genetic disorder characterized by significant obesity and presum ed hypothalamic dysfunction. The potential interaction of leptin metabolism with the growth hormone (GH) axis was also studied. STUDY DESIGN Plasma leptin concentrations and percent body fat were determi ned by radioimmunoassay and dual energy x-ray absorptionmetry, respectively , in 23 children with Prader-Willi syndrome and 23 children with exogenous obesity. RESULTS Log plasma leptin concentrations were positively correlated with pe rcentage body fat in PWS (r = 0.844) and exogenous obesity (r = 0.869). Whe n the regression lines for the two groups were compared, there were no diff erences in their slopes (P = 0.737) or intercepts (P = 0.701). Administrati on of recombinant human growth hormone to PWS children for 12 months signif icantly reduced both percentage body fat and plasma leptin concentrations, but the relationship of log plasma leptin to percentage body fat was unchan ged. CONCLUSIONS Prader-Willi syndrome is not accompanied by deranged leptin con centrations and there was no evidence of an interaction of the GH axis with leptin metabolism in these GH-deficient children.