Leptin sexual dimorphism, insulin resistance, and body composition in normal weight prepubescent

The prepubertal stage is a critical period of body fat development, in which leptin and insulin resistance has been associated, however, there are few studies in normal-weight prepubescents. Objective: To assess the relationship between leptin and body composition and insulin resistance in a group of normal-weight prepubescents. Patients and Method: Analytical cross-sectional study with 128 healthy prepubescents of normal weight, aged between 6 and 10 years. Height, weight, body mass index (BMI), body fat percentage (BFP), waist circumference (WC), and hip circumference (HC) were measured. Plasma leptin (ng/mL) and insulin (mU/L) were evaluated by immunoassay and glycemia (mmol/L) by enzymatic method. HOMA-IR was calculated. A comparison study and correlation analysis by sex were performed. Results: Females presented higher values than males of leptin (6.8 +/- 5 vs 3.3 +/- 3.7; p = 0.000), insulin (7.1 +/- 4.5 vs 5.2 +/- 2.5; p = 0.016), BFP (22.4 +/- 4.3 vs 18.6 +/- 3.9; p = 0.000), and HC (67 +/- 5.7 vs 65.0 +/- 4.5; p = 0.019), and a lower waist/hip ratio (0.84 +/- 0.04 vs 0.88 +/- 0.04; p = 0.000). Leptin correlations with anthropometric variables were significant in both sexes, with greater association in females. The association of HOMA-IR with leptin was similar in both sexes. Conclusions: in normal-weight prepubescents aged between 6-10 years, there are sex differences in adiposity and leptin levels not associated with differences in BMI or insulin resistance. The greater association of leptin with adiposity in girls could be related to a high rate of adipogenesis induced by this hormone.