Sex hormone-binding globulin as a marker for hyperinsulinemia and/or insulin resistance in obese children

Objective: A relationship between hyperinsulinemia and decreased serum sex hormone-binding globulin (SHBG) has been described in adults. We evaluated the usefulness of SHBG as an index of hyperinsulinemia and/or insulin resis tance in obese children (aged 6-9 years) of both sexes and its possible inf luence on the androgenic status. Design: We carried out a cross-sectional study of cases and controls. We st udied 61 obese children (22 males, 39 females) with body mass index (BMI) s uperior to the 90(th) percentile and a control group of age- and sex-matche d non-obese children. We measured serum glucose, insulin, TSH, free thyroxi ne, 17 beta-estradiol, testosterone and SHBG. Also, we correlated these par ameters with anthropometric measures. Results: The obese group presented significantly elevated levels of insulin (P = 0.001) and insulin/ glucose ratio (P = 0.0012) compared with the cont rol group. SHBG (P = 0.0001) and testosterone (P = 0.0169) levels were sign ificantly lower than those in the non-obese group. We did not End any diffe rence in the free androgen index (FAI). Fasting insulin (r = -0.4512; P < 0 .001), BMI (r = -0.3185; P < 0.05) and testosterone (r = -0.3705; P < 0.01) were inversely correlated with SHBG concentration. According to multivaria te analyses, insulin was the only independent predictor factor for serum SH BG concentration in the obese group (r partial = 0.1280: P = 0.0171). Conclusions: In summary at this age there is a strong relationship between insulin and SHBG. The changes in SHBG levels of the obese group did not aff ect FAI and, therefore, they did not cause changes in the androgenic status . Our data support the role of insulin in the regulation of serum SHBG leve ls.