Association Between Thyroid Hormone Sensitivity and Non-Alcoholic Fatty Liver Disease in Individuals with Normal Thyroid Function.

Introduction: Nonalcoholic fatty liver disease (NAFLD) is a globally prevalent metabolic disorder that has attracted increasing clinical and public health attention. Although several studies have suggested a potential link between thyroid hormone levels and the risk of NAFLD, existing epidemiological evidence remains limited and inconsistent. Therefore, this study aims to investigate the association between thyroid hormone sensitivity and NAFLD in individuals with normal thyroid function. Furthermore, we sought to explore whether this association differs according to the presence or absence of metabolic comorbidities, particularly type 2 diabetes mellitus (T2DM) and non-diabetic (non-DM) status.

Methods: We included 460 adults with normal thyroid function, comprising 229 patients with T2DM and 231 without diabetes. Steatosis was assessed using liver ultrasonography.

Results: Both the thyroid feedback quantile index based on free thyroxine (TFQI-FT4) and that based on free triiodothyronine (TFQI-FT3) were positively associated with the presence of NAFLD (Q4 vs Q1, Model 3: TFQI-FT4, OR = 3.290, 95% CI: 1.390-7.787, p = 0.007; TFQI-FT3, OR = 2.344, 95% CI: 1.010-5.439, p = 0.047). Among individuals with type 2 diabetes mellitus (T2DM), a higher FT3/FT4 ratio was associated with a lower risk of NAFLD (Q3 vs Q1, Model 2: OR = 0.221, 95% CI: 0.053-0.921, p = 0.038), although the comparison between Q4 and Q1 did not reach statistical significance (OR = 0.402, 95% CI: 0.100-1.614, p = 0.199). In contrast, among non-diabetic individuals, a higher FT3/FT4 ratio was positively associated with NAFLD (Q4 vs Q1, Model 2: OR = 3.390, 95% CI: 1.003-11.463, p = 0.049).

Conclusion: Thyroid hormone sensitivity is associated with the development of NAFLD development in individuals with normal thyroid function and may be influenced by the presence of T2DM.