Association Between Sensitivity to Thyroid Hormones and Metabolic Dysfunction-Associated Fatty Liver Disease in Euthyroid Subjects: A Cross-Sectional Study

OBJECTIVE: Thyroid hormones (THs) exert instrumental effects in regulating lipids metabolism. Whereas, research investigating the relationship between sensitivity indices to THs and metabolic dysfunction-associated fatty liver disease (MAFLD) have contradicted this. This study was designed to approach the correlation between sensitivity indices to THs and MAFLD in euthyroid subjects. METHODS: An overall sample of 6356 euthyroid participants were enrolled in a Chinese hospital. Free triiodothyronine to free thyroxine ratio (FT3/FT4), thyrotropin triiodothyronine resistance index (TT3RI), thyrotropin thyroxine resistance index (TT4RI), thyroid stimulating hormone index (TSHI) and thyroid feedback quantile-based indices (TFQI(FT3) and TFQI(FT4)) were collected as sensitivity indicators to THs. Participants were split into two groups based on whether they suffered with MAFLD or not. And participants were categorized into quartiles based on sensitivity indicators to THs. The effects of sensitivity indices to THs on MAFLD were analyzed using regression analysis. Bootstrap was performed to assess the mediation effect of triglyceride glucose (TyG) index on the relationship between sensitivity parameters to THs and MAFLD. RESULTS: The incidence of MAFLD in euthyroid subjects was 34.47%. As FT3/FT4, TT3RI and TFQI(FT3) levels rose, so did the MAFLD prevalence. After adjustment for confounders, logistic regression analyses indicated that the high-level FT3/FT4 and TFQI(FT3) still remained risk factors for MAFLD. The relevance of FT3/FT4 and MAFLD was stronger among those whose age ≤ 40 years and had non-visceral obesity. And the interrelation between TFQI(FT3) and MAFLD was stronger in subjects whose age ≤ 40 years. Mediation analyses suggested that TyG index had a noteworthy indirect impact on the relationship between FT3/FT4, TFQI(FT3) and MAFLD. CONCLUSION: Increased FT3/FT4 and TFQI(FT3) were significantly related to MAFLD prevalence in populations with normal thyroid function. TyG index partly mediated the relevance between FT3/FT4, TFQI(FT3) and MAFLD.