Relationship of thyroid function with body mass index, insulin-resistance and lipid status in nutritionally obese children and adolescents.

Background: In recent years, there has been an increasing attention to thyroid function in paediatric obese patients due to its possible role as metabolic and cardiovascular risk factor. Objectives: a) to ascertain the association between thyroid function, lipid status and insulin resistance (IR) in nutritionally obese children and adolescents; 2) to evaluate the frequency of hyperthyrotropinemia in our cohort. Design: Cross-sectional study. Methods: We examined 311 obese children and adolescents (163 females), mean age 9.2 ± 2.8 yrs (62.7% prepubertal) from a iodine sufficient region. Anthropometric, metabolic and hormonal variables were determined when patients were referred to our Outpatients Clinic during the period 2005-2010. Patients with thyroid autoimmune disease (TAD) and/or other chronic diseases were excluded. Results: Hyperthyrotropinemia (TSH >4.5 mIU/L) was diagnosed in only 9 cases (2.9%, 2 females). In the remaining 302 euthyroid subjects (161 females) we did not find any correlation between TSH levels and BMI-SDS, lipid panel and IR. Conversely, FT4 levels were correlated with both BMI-SDS (r=0.139, p=0.016) and HDL cholesterol levels (r=-0.150, p=0.018). There were no differences of FT4 levels, lipid status and HOMA-IR between patients with TSH <2.5 mIU/L and those with TSH 2.5 - 4.5 mIU/L. Among the 187 prepubertal children, HOMA-IR was significantly higher in the 130 subjects with TSH between 2.5 and 4.5 mIU/L compared with those with TSH <2.5 mIU/L (3.41 ± 2.87 vs 2.60 ± 1.92, p = 0.026). No differences were found in pubertal adolescents. Conclusions: In our paediatric obese population: 1) the prevalence of hyperthyrotropinemia resulted only slightly higher than that reported in general paediatric population (2.9 vs 1.7%), probably due to the preliminary exclusion of subjects with TAD; 2) TSH levels were not correlated with the severity of the obesity; 3) among the euthyroid prepubertal obese children insulin sensitivity was significantly lower in the subgroup with TSH between 2.5 and 4.5 mIU/L.