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

Abstract

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 resistance in obese children (aged 6-9 years) of both sexes and its possible influence on the androgenic status. We carried out a cross-sectional study of cases and controls. We studied 61 obese children (22 males, 39 females) with body mass index (BMI) superior to the 90(th) percentile and a control group of age- and sex-matched non-obese children. We measured serum glucose, insulin, TSH, free thyroxine, 17beta-estradiol, testosterone and SHBG. Also, we correlated these parameters with anthropometric measures. The obese group presented significantly elevated levels of insulin (P=0.001) and insulin/glucose ratio (P=0.0012) compared with the control group. SHBG (P=0.0001) and testosterone (P=0.0169) levels were significantly lower than those in the non-obese group. We did not find any difference 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 multivariate analyses, insulin was the only independent predictor factor for serum SHBG concentration in the obese group (r partial=0.1280; P=0.0171). 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 affect 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 levels.