Hyperthyrotropinemia in overweight and obese children is associated with higher insulin resistance

Abstract

Background: Elevated thyroid-stimulating hormone (TSH) with normal thyroid hormone levels is found in up to 23% of obese children and correlates positively with body mass index (BMI). It seems to be rather a consequence than a cause of obesity. The aim of this study was to investigate the association between TSH levels and insulin resistance in overweight and obese children. Methods: Study included 289 overweight (OW) (BMI-SDS >1.0) and obese (OB) (BMI-SDS >2.0) children, mean age 13.5 2.0 years; 43.3% were males. Mean BMI-SDS was 2.46 0.8, 76.5% were obese. BMI was evaluated according to IOTF criteria for children. OGTT with analysis of glucose and insulin concentrations at 0, 30 and 120 minutes was performed; TSH, free thyroxine (FT4) and anti-TPO levels were determined from baseline blood samples. Children with increased anti-TPO levels were excluded from further analysis. Results: Increased TSH (>4.0 IU/l) levels were found in 13.7% of OW/OB children and adolescents. BMI-SDS and waist circumference (WC)-SDS were significantly higher in children with increased TSH compared to children with normal TSH levels (mean 2.67 0.8 vs. 2.39 0.8, p < 0.001 and 1.7 0.7 vs. 1.5 0.7, p < 0.001, respectively). Insulin concentrations at 0, 30 and 120 min. of OGTT were significantly higher is children with increased TSH concentration (mean 21.1 8.9 vs. 16.9 7.8 mIU/l, p < 0.005, 148.2 65.8 vs. 114.7 69.5 mIU/l, p < 0.026 and 85.8 66 vs. 67.5 56.5 mIU/l, p < 0.008, respectively). HOMA-IR was significantly higher is those children who had increased TSH compared to those with TSH levels (4.91 2.3 vs. 3.86 1.9, p < 0.002, respectively). Glucose concentrations were similar in both groups. Conclusions: OW/OB children with incresed TSH levels (>4 IU/ml) have higher BMI-SDS and WC-SDS, and are more insulin resistant than children with normal TSH levels.