Free T4 is Negatively Correlated with Non-alcoholic Fatty Liver Disease in Euthyroid Women

Background: Thyroid hormones play an important role in the regulation of lipid and carbohydrate metabolism and the body mass index (BMI), which all affect non-alcoholic fatty liver disease (NAFLD). In a previous study, we demonstrated that free T4 was negatively associated with the BMI in euthyroid women. However, there is still uncertain as to whether the thyroid function within the normal range is associated with NAFLD and liver function abnormalities. We sought to evaluate the thyroid function (free T4, TSH) and its possible relationship with NAFLD in euthyroid women. Methods: A total of 835 euthyroid, non heavy alcoholics women who visit ed the Daegu Catholic University University Medical Centre for primary health screening from January 1, 2006 to December 31, 2006 participated in this cross-sectional study. The women who were not euthyroid or heavy alcoholics (> 70 g/week in women according to the DSM-IV), there was no known history of diabetes mellitus, the fasting blood glucose was more than 5.55 mmol/L and those who had viral hepatitis were excluded. Hepatic ultrasonography scanning was performed in all the participants by a single experienced radiologist. The TSH, free T4, BP, fasting glucose, serum liver enzymes (AST, ALT, GGT, T-bilirubin), lipid profiles [total-cholesterol, triglyceride (TG), HDL-C, LDL-C] and NAFLD were evaluated. Results: Euthyroid women with NAFLD had lower free T4 levels than did the euthyroid women without NAFLD. After adjustment for age and BMI, free T4 was negatively correlated with TG, but free T4 was positively correlated with the total serum bilirubin. Free T4 was not correlated with the serum AST, ALT and GGT. After adjustment for age, the BMI, the fasting glucose, the GGT and free T4, but not TSH, were significantly negatively correlated with NAFLD. Conclusion: We demonstrated a negative correlation between free T4 and NAFLD in euthyroid women. This finding suggests lower levels of free T4 is associated with NAFLD in euthyroid subjects. (J Korean