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 secretio n, leptin concentrations, and body composition measured with x-ray absorpti ometry (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 weigh t for height so scores (WHSDS) was 0.2 (1.18). Body composition was investi gated using DXA. Blood samples were taken for analysis of leptin, insulin-l ike 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 = 0.8 3; 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 bet ween 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 th is disappeared after adjustment for body fat, as measured by DXA. There wer e 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 a rea under the curve above the calculated baseline, and GH(max) is the maxim um 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 reg ression analysis with leptin as the dependent variable, the percent trunk f at accounted for 77.7% of the leptin variation. With AUC(b) for GH as the d ependent variable, the percent trunk fat accounted for 20.3% of the variati on. 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 th e percentage of fat from arms and legs for another 4.4%. We demonstrated a strong positive correlation between leptin levels and bod y fat, a significant negative correlation between leptin levels and GH secr etion, and a significant negative correlation between body fat and GH secre tion. We have also shown that specific regional fat depots have different r elationships with leptin and particular markers of GH secretion.