GENDER AND TANNER STAGE DIFFERENCES IN BODY-COMPOSITION AND INSULIN SENSITIVITY IN EARLY PUBERTAL CHILDREN

A cross-sectional analysis examining the impact of gender and early pu bertal stage on insulin sensitivity (Si) and body composition was carr ied out as part of a longitudinal study to determine how Si relates to body composition changes during puberty. The study population consist ed of 97 healthy children (age range, 9.7-14.5 yr; 28 Tanner stage 2 b oys, 25 stage 3 boys, 22 Tanner stage 2 girls, and 22 stage 3 girls). Si was determined by the modified minimal model of Bergman. Body fatne ss was assessed by body mass index (BMI), skinfold thickness, hydroden sitometry, and bioelectrical impedance. Results showed that stage 3 gi rls and stage 2 boys had significantly more body fat than stage 2 girl s and stage 3 boys. Si was significantly lower (P < 0.02) and insulin- like growth factor-I levels higher (P < 0.006) in stage 3 girls compar ed to those in the other 3 groups. The best predictor of Si in all sub jects was BMI (r(2) = -0.63; P < 0.0001). In a stepwise multiple regre ssion analysis, Si was best predicted from BMI, gender, and Tanner sta ge. According to this model, Si decreased as BMI increased and was low er in girls and Tanner stage 3 children. In boys, Si was best predicte d from total fat mass and Tanner stage. In girls, Si correlated invers ely with BMI, parental obesity, and insulin-like growth factor-I level s. Neither testosterone nor estradiol levels were associated with Si. These results demonstrate that Si, like body composition, has gender-d ependent changes during puberty. It is, thus, possible that these pube rtal changes in Si relate to changes in body composition.