Circulating leptin level and growth hormone response to stimulation tests in obese and normal children

Objective: Growth hormone secretion is decreased in obese subjects, and their GH response to stimulation tests is blunted. The mechanisms relating excess adipose mass and GH secretion are unknown. We hypothesized that leptin might be a signal linking adipose mass to GH secretion, Design: We measured serum leptin levels and the GH response to stimulation tests in 42 obese and 40 lean short normal prepubertal children. Results: The mean serum leptin concentrations were 23.8 +/- 1.7 ng/ml and 3.6 +/- 0.4 ng/ml in obese and lean children respectively, and were found to be inversely related to GH peak in both groups, After adjusting for body fat data, leptin was still an independent predictor of GH peak. Multiple stepwise regression analysis identified both leptin (regression coefficient= -0.78, P=0.001), and insulin (regression coefficient = - 0.03, P = 0.009) as negative determinants of GH response to the GHRH test in obese children (multiple R = 0.64), and only leptin in lean children (r= - 0.51, P = 0.001). No correlation was observed between leptin and IGF-I or IGF binding protein-3. Conclusion: These results are consistent with the hypothesis that leptin could contribute to the regulation of GH secretion.