Associations among FT4 level, FT3/FT4 ratio, and non-alcoholic fatty liver disease in Chinese patients with hypopituitarism

Non-alcoholic fatty liver disease (NAFLD) is the most common hepatic metabolic disorder. Thyroid function is associated with NAFLD in different populations; however, little attention has been paid in patients with hypopituitarism. To analyze the association between thyroid function and NAFLD, we included 134 patients with hypopituitarism admitted to the Tianjin Medical University General Hospital between June 2013 and May 2019. Participants were divided into the NAFLD(-) and NAFLD(+) groups based on abdominal ultrasonography findings. We evaluated 68 male and 66 female patients with hypopituitarism. The prevalence of NAFLD was 52.24%. The NAFLD(+) group had a significantly higher free triiodothyronine/free thyroxine (FT3/FT4) ratio than the NAFLD(-) group (p = 0.003). The NAFLD(+) group showed significantly lower levels of FT4 and the growth hormone (GH) than the NAFLD(-) group (p = 0.003 and 0.016, respectively). We observed an association of the FT4 level and FT3/FT4 ratio with NAFLD in the univariate model, which was non-significant after adjustment for metabolic parameters (BMI, HDL-C, triglycerides, serum uric acid, blood pressure, fasting glucose). To better understand the role of each metabolic parameters, we performed additional models for each of those predictors individually after adjustment for age and gender, the association between FT4 level and FT3/FT4 ratio lost significance after adjustment for HDL-C and TG, but not for other predictors. Our findings suggest that thyroid dysfunction may be crucially involved in NAFLD by regulating whole-body metabolism, especially lipid utilization. Therefore, sufficient thyroid hormone replacement therapy for patients with hypopituitarism is recommended from the early stage.