RESUMO
PURPOSE:There is a clear sexual dimorphism in circulating concentration of leptin in adulthood. However, we don' know when such dimorphism begins and how much pubertal development influences on it. So we examined body composition and circulating concentrations of leptin according to Tanner stage(TS). METHODS:We examined 112 children(M; 56, F; 56, Age; 8.5-17 yr) to evaluate the relationship of leptin and body composition. Body composition was determined by bioelectric impedence measurements(BIA) and by anthropometry. Leptin was measured by human specific RIA. Leptin level was analysed according to TS, body mass index(BMI), fat mass(FM), and lean body mass. RESULTS:BMI and free FM was correlated with TS in both sexes. FM was closely correlated with TS in girls but not in boys(M; r=0.08, P=0.54. F; r=0.73, P>0.001). Leptin levels increased in girls with advanced TS(r=0.355, P<0.01), but decreased in boys(r=-0.339, P<0.01). A strong exponential relationship was observed for leptin levels with BMI, FM, and percentage body fat as determined by BIA. There was significant sexual dimorphism of leptin level at TS VI/V. Because leptin level was significantly related FM, leptin level was normalized to FM(Leptin/FM). Leptin/FM of females(0.67+/-.27 ng/mL/kg) was also significantly higher then that of males(0.31+/-.15 ng/mL/kg)(P<0.001). CONCLUSION: These data suggest that plasma leptin levels increase in girls and decrease in boys after TS II as pubertal development proceeds; they show a significant gender difference, especially late puberty, even after adjustment for FM. Sexual dimorphism in leptin during puberty reflects not only differential changes in body composition but also different leptin resistance; reference ranges of leptin could be modified by TS and gender.
Assuntos
Adolescente , Criança , Feminino , Humanos , Tecido Adiposo , Antropometria , Composição Corporal , Leptina , Plasma , Puberdade , Valores de ReferênciaRESUMO
PURPOSE:There is a clear sexual dimorphism in circulating concentration of leptin in adulthood. However, we don' know when such dimorphism begins and how much pubertal development influences on it. So we examined body composition and circulating concentrations of leptin according to Tanner stage(TS). METHODS:We examined 112 children(M; 56, F; 56, Age; 8.5-17 yr) to evaluate the relationship of leptin and body composition. Body composition was determined by bioelectric impedence measurements(BIA) and by anthropometry. Leptin was measured by human specific RIA. Leptin level was analysed according to TS, body mass index(BMI), fat mass(FM), and lean body mass. RESULTS:BMI and free FM was correlated with TS in both sexes. FM was closely correlated with TS in girls but not in boys(M; r=0.08, P=0.54. F; r=0.73, P>0.001). Leptin levels increased in girls with advanced TS(r=0.355, P<0.01), but decreased in boys(r=-0.339, P<0.01). A strong exponential relationship was observed for leptin levels with BMI, FM, and percentage body fat as determined by BIA. There was significant sexual dimorphism of leptin level at TS VI/V. Because leptin level was significantly related FM, leptin level was normalized to FM(Leptin/FM). Leptin/FM of females(0.67+/-.27 ng/mL/kg) was also significantly higher then that of males(0.31+/-.15 ng/mL/kg)(P<0.001). CONCLUSION: These data suggest that plasma leptin levels increase in girls and decrease in boys after TS II as pubertal development proceeds; they show a significant gender difference, especially late puberty, even after adjustment for FM. Sexual dimorphism in leptin during puberty reflects not only differential changes in body composition but also different leptin resistance; reference ranges of leptin could be modified by TS and gender.