LEPTIN LEVELS AND BODY FATNESS IN CHILDREN - EFFECTS OF GENDER, ETHNICITY, AND SEXUAL DEVELOPMENT

Leptin, a hormone secreted by adipocytes, is elevated in blood of obes e adults, It is unknown whether the concentration is affected by gende r, ethnicity, age, or stage of sexual maturation in children. We measu red serum leptin levels in 183 children and 27 young adults using a do uble-antibody ELISA assay, Body fat mass (FM) and percent body fatness (%Fat) were determined by dual-energy x-ray absorptiometry, Correlati ons for serum leptin with FM, %Fat, and a body mass index were examine d. Analyses of covariance were used to determine the effects of Fender ethnicity, and sexual maturation (Tanner stage). We found strong posi tive correlations (r=0.56-0.88,p<0.001) for serum leptin with body mas s Index, %Fat, and FM, which were gender-dependent (p<0,001), but unaf fected by ethnicity, Al each Tanner stage, female subjects had higher serum leptin than male subjects (p < 0.001), and this difference remai ned significant (p < 0.001) when leptin was normalized for FM, For eac h gender, the mean leptin/FM ratios were relatively invariant during s exual maturation and no differences were observed between the oldest c hildren (Tanner stage 5) and the young adults, The observation that fe male subjects have higher mean serum leptin and leptin/FM levels than male subjects Lit prepubertal ages may suggest that there are gender d ifferences in leptin synthesis, clearance rates, bioactivity, and/or l eptin transport.