Metabolic, cardiovascular and anthropometric differences between prepubertal girls and boys.

OBJECTIVE: We aimed to assess possible differences in insulin sensitivity and other metabolic, anthropometric and cardiovascular parameters between boys and girls prior to puberty.
METHODS: We studied 85 healthy prepubertal children (33 girls and 52 boys) aged 8.7 ± 1.9 years (range 4.0-11.9 years), born 38-40 weeks gestation, and of birth weight appropriate-for-gestational-age. Insulin sensitivity was measured using frequently sampled intravenous glucose tests and Bergman's minimal model. Other clinical assessments included anthropometric measures, fasting lipid and hormonal profiles, body composition from whole-body dual-energy X-ray absorptiometry and 24-h ambulatory blood pressure monitoring.
RESULTS: Prepubertal girls and boys were of similar parent-adjusted height SDS (P = 0.26), but girls had considerably more body fat (P < 0.0001), less fat-free mass (P = 0.0002) and greater abdominal adiposity (P < 0.0001). These differences in body composition were independent of adrenal androgens. Insulin sensitivity was 18% lower in girls (11.0 vs 13.4 × 10(-4) /min (mU/l); P = 0.028), but this difference disappeared with adjustment for adiposity and DHEAS concentrations. There were, however, some apparent sex differences in cardiovascular parameters, with girls displaying increased heart rate and reduced blood pressure dipping. Girls also had higher triglyceride concentrations (+23%; P = 0.036).
CONCLUSION: There are a number of anthropometric, metabolic and cardiovascular differences between sexes prior to the appearance of external signs of puberty. Although differences in insulin sensitivity were eliminated when adiposity and DHEAS concentrations were accounted for, there were independent differences in body composition and cardiovascular parameters. Thus, gender, adrenarche and adiposity should be accounted for in studies examining metabolic and cardiovascular outcomes prior to puberty.