Association Between Thyroid Function and Metabolic Dysfunction-Associated Fatty Liver Disease in Patients with Type 2 Diabetes Mellitus: A Case-Control Study.

Background: Metabolic dysfunction-associated fatty liver disease (MAFLD) is highly prevalent among patients with type 2 diabetes mellitus (T2DM) and is closely linked to metabolic disturbances such as insulin resistance and dyslipidemia. Thyroid hormones play a critical role in regulating hepatic lipid metabolism and energy homeostasis; however, their relationship with MAFLD in diabetic populations remains incompletely defined. Methods: In this case-control study, 150 patients with T2DM were enrolled, including 75 patients with MAFLD and 75 without MAFLD. Hepatic steatosis was confirmed using transient elastography with controlled attenuation parameter (CAP). Serum free triiodothyronine (FT3), free thyroxine (FT4), and thyroid-stimulating hormone (TSH) were measured using chemiluminescent immunoassays. Clinical, anthropometric, and biochemical parameters were assessed. Multivariate logistic regression analysis was performed to identify independent predictors of MAFLD. Results: Patients with MAFLD had significantly lower FT3 levels and higher TSH levels compared with diabetic controls without MAFLD (p = 0.016 and p < 0.001, respectively), while FT4 levels were comparable between groups. MAFLD was also associated with an adverse metabolic profile, including elevated triglycerides, total cholesterol, and low-density lipoprotein cholesterol, along with reduced high-density lipoprotein cholesterol (all p < 0.001). Liver enzymes were significantly higher in the MAFLD group. In multivariate analysis, elevated TSH (OR = 3.62, 95% CI: 1.21-10.84, p = 0.021) and triglycerides (OR = 1.43, 95% CI: 1.14-1.80, p = 0.002) were independently associated with MAFLD, whereas FT3 was not independently associated after adjustment. Conclusions: Elevated TSH levels are independently associated with MAFLD in patients with T2DM, suggesting a link between thyroid function and hepatic steatosis beyond traditional metabolic risk factors. These findings highlight the potential role of thyroid function, particularly TSH, in the metabolic risk stratification of patients with diabetes and warrant further investigation into thyroid-liver interactions.