['To examine whether obesity, body fat distribution and insulin resistance have an independent effect on serum TSH and free thyroid hormones (FT3 and FT4) in a cohort of euthyroid women, represented by overweight and obese patients.', 'A total of 201 women, aged 18-68 years, with body mass index (BMI) > or = 25.0 kg/m(2) and TSH levels < 4.0 mU/l were investigated.', 'Fasting TSH, FT3, FT4, insulin, glucose, and serum lipid concentrations, and the level of insulin resistance, estimated by the homeostasis model assessment for insulin resistance (HOMA-IR). Waist circumference was measured as an indirect parameter of central fat accumulation.', 'FT3 was directly associated with BMI (P < 0.01) and waist circumference (P < 0.01), and negatively correlated with age (P < 0.001). FT4 was negatively associated with HOMA-IR (P < 0.05) and fasting insulin levels (P < 0.05). TSH was positively correlated with waist circumference (P < 0.05) and negatively associated with age (P < 0.05). When multiple regression analysis was performed with FT3 as the dependent variable, and waist circumference, HOMA-IR, blood pressure levels and serum lipid concentrations as independent variables, FT3 maintained an independent association only with waist circumference (positive, P < 0.05) and age (negative, P < 0.001). When multiple regression analysis was performed with TSH as the dependent variable, and the above parameters as independent variables, TSH maintained an independent association only with waist circumference (positive, P < 0.05) and age (negative, P < 0.05). By contrast, when multiple regression analysis was performed with FT4 as the dependent variable, FT4 did not maintain an independent association with any of the independent parameters.'] Are free triiodothyronine and thyroid stimulating hormone directly associated with waist circumference , independently of insulin resistance , metabolic parameters and blood pressure in overweight and obese women?