The distribution of abdominal fat is correlated with thyrotrophin and free triiodothyronine level

Objective To analysis the correlation between thyroid function and abdominal subcutaneous fat and visceral fat determined by magnetic resonance image (MRI) scnning, and to investigate the influence of thyroid function on abdominal fat distribution. Methods 763 residents aged between 40 and 65 years old were randomly selected from South Station community. A detailed questionnaire and physical examination, height, weight, waist circumference, hip circumference, blood pressure was conducted. Body mass index and waist to hip ratio were calculated.Tanita TBF 300Abody fat component instrument was used to measure body fat. Fasting blood was collected to test fasting blood glucose, total cholesterol, triglycerides, high density lipoprotein cholesterol, low-density lipoprotein cholesterol, fasting insulin, TSH, FT4, FT3 and TPOAb. Oral glucose tolerance test was performed. MRI scan was conducted to measure the subcutaneous fat (SF) and visceral fat (VF) area. Results Pearson correlation analysis showed that LnTSH and SF were positively correlated (r=0.183, P<0.05), but no correlation was found between LnTSH and VF. FT4 and SF were negatively correlated (r=-0.164, P<0.05), and FT4 was positively correlated with VF (r=0.118, P<0.05). FT3 and SF were negatively correlated (r=-0.098, P<0.05), and FT3 was positively correlated with VF (r=0.261, P<0.05). Variables relevant to SF or VF area in single correlation model were put into the regression model, and the results showed that systolic blood pressure (SBP), LnTSH and FT3 were risk factors of SF area. While BMI, waist circumference, blood uric acid and OGTT 2 h blood glucose were risk factors of VF area. Conclusion The cross-sectional epidemiological study showed serum TSH elevation and FT3 decrease were risk factors of SF area, which indicated serum TSH and FT3 may play a certain role in the distribution of body fat. Key words: Thyrotrophin; Free thyroxinelndex; Free triiodothyronine; Subcutaneous fat; Visceral fat