Endocrine Abstracts

Objective: Thyroid function tests (TFTs) have been associated with obesity; however associations with the type of adiposity have not been examined. Ultrasound (U/S) was used to assess regional adiposity in euthyroid individuals. Associations of thyroid function with obesity parameters and presence of the metabolic syndrome (MS) were investigated.

Methods: Of 302 apparently healthy slightly overweight individuals (age 42.9±8.8, BMI 19.0–43.3, median 26.2 kg/m², 180 women) were examined for indices of the metabolic syndrome (MS). Abdominal subcutaneous (SF) and pre-peritoneal (PF) fat layer was estimated by US. BMI, waist and hip circumference were recorded; TSH, T₃, thyroid autoantibodies, insulin, glucose and lipid levels were measured.

Results: T₃ levels were positively associated with PF (r=0.245, P=0.004), SF (r=0.189, P=0.019), BMI (r=0.257, P=0.0004), waist perimeter (r=0.324, P<0.0001) and waist-to-hip-ratio (r=0.363, P<0.0001). TSH levels correlated with SF (r=0.146, P=0.039). Higher TSH levels were associated with higher total cholesterol and LDL levels (P=0.008). HOMA-insulin-resistance-index and BMI were higher among individuals with TSH>2.5 mU/l compared to those with TSH≤2.5 mU/l, P=0.048). TFTs did not differ between those with MS and those without.

Conclusions: Increased subcutaneous and pre-peritoneal fat accumulation is associated with higher T₃ levels in euthyroid slightly overweight individuals; this may represent a compensatory mechanism for the increased abdominal fat accumulation, as has been described in morbid obesity. The positive association of higher levels of TSH with SF may reflect associations with a mild hypothyroid state or possibly resistance to thyroid hormones as has previously been suggested.