Serum leptin levels correlate with growth hormone secretion and body fat in children

The aim of this study was to investigate the relationship among GH secretion, leptin concentrations, and body composition measured with x-ray absorptiometry (DXA) in children. In total, 71 children were investigated, 51 males and 20 females. Their mean chronological age was 10.8 yr (range, 6.2-17.7 ys), and their mean height (SD) was -2.1 (0.63) SD scores. Their mean weight for height so scores (WHSDS) was 0.2 (1.18). Body composition was investigated using DXA. Blood samples were taken for analysis of leptin, insulin-like growth factor I (IGF-I), IGF-binding protein-3, and 24-h GH secretion. A positive correlation was found between leptin and total body fat (r = 0.83; P < 0.0001) and when fat was expressed as a percentage of body weight (r = 0.86; P < 0.0001). There were significant (P < 0.0001) relationships between leptin and WHSDS (r = 0.45) and between leptin and body mass index (r = 0.69). A significant gender difference in leptin levels was found, but this disappeared after adjustment for body fat, as measured by DXA. There were significant (P < 0.001) inverse correlations between leptin and the AUC(b) for GH (r = -0.41), leptin, and GH(max) (r = -0.38) where AUC(b) is the area under the curve above the calculated baseline, and GH(max) is the maximum peak during the 24-h GH profile (percent fat; and AUC(b) for GH, r = -0.43; percent fat and GH(max), r = -0.39). In a multiple stepwise forward regression analysis with leptin as the dependent variable, the percent trunk fat accounted for 77.7% of the leptin variation. With AUC(b) for GH as the dependent variable, the percent trunk fat accounted for 20.3% of the variation. With GH(max) as the dependent variable, the percent trunk fat accounted for 18.8% of the variation, IGF-binding protein-3 for another 8.5%, and the percentage of fat from arms and legs for another 4.4%. We demonstrated a strong positive correlation between leptin levels and body fat, a significant negative correlation between leptin levels and GH secretion, and a significant negative correlation between body fat and GH secretion. We have also shown that specific regional fat depots have different relationships with leptin and particular markers of GH secretion.