Low-Normal Thyroid Function Is Not Associated with Either Non-Alcoholic Fatty Liver Disease or with Metabolic Dysfunction-Associated Fatty Liver Disease

Background: The association of low-normal thyroid function (LNTF) with non-alcoholic fatty liver disease (NAFLD) or metabolic dysfunction-associated fatty liver disease (MAFLD) is controversial; thus, the aim of this study is to determine this association. Methods: NAFLD was evaluated by controlled attenuation parameter of transient elastography. Patients were classified by MAFLD criteria. LNTF was defined as TSH levels of 2.5 to 4.5 mIU/L and were divided into three different cut-off points (>4.5 to 5.0, >3.1, and >2.5 mIU/L). Associations between LNTF, NAFLD, and MAFLD were evaluated by univariate and multivariate logistic regression analyses. Results: A total of 3697 patients were included; 59% (n = 2179) were male, and median age and body mass index were 48 (43-55) years and 25.9 (23.6-28.5) kg/m(2), respectively, and 44% (n = 1632) were diagnosed with NAFLD. THS levels of 2.5 and 3.1 showed significant associations with the presence of NAFLD and MAFLD; however, LNTF did not show an independent association with the presence of NAFLD or MAFLD in multivariate analysis. According to different cut-off points, patients with LNTF presented similar risks for NAFLD as the general population. Conclusion: LNTF is not associated with NAFLD or MAFLD. Patients with high LNTF are equally at risk for NAFLD as the general population.