Exploring the causal relationship between Hashimoto thyroiditis and metabolic-associated fatty liver disease: A Mendelian randomization study

This study aims to investigate the possible causal link between Hashimoto thyroiditis (HT), an autoimmune disorder, and metabolic-associated fatty liver disease (MAFLD), previously referred to as nonalcoholic fatty liver disease (NAFLD), a common metabolic condition. Using genome-wide association study data from large European populations, we performed a bidirectional Mendelian randomization (MR) analysis. We identified single nucleotide polymorphisms strongly associated with HT and MAFLD/NAFLD, which we used as instrumental variables to probe the causal relationship between these 2 conditions. The forward MR analysis, using the inverse variance weighted method, showed that HT may increase the risk of MAFLD/NAFLD (odds ratio = 1.065, 95% confidence intervals: 1.014-1.119, P = .011). However, the reverse MR analysis did not establish a significant causal effect of MAFLD/NAFLD on HT (P > .05). Sensitivity analyses were carried out to assess potential heterogeneity or pleiotropy, and the results supported the robustness of our findings, indicating no significant concerns. These results suggest that HT may be a risk factor for the development of MAFLD/NAFLD. The bidirectional MR study revealed an elevated risk of MAFLD/NAFLD in individuals with HT, but no causal relationship was found from MAFLD/NAFLD to HT in the opposite direction. This understanding could assist healthcare professionals in improving their comprehension and management of both HT and MAFLD/NAFLD, leading to more comprehensive clinical guidance for patients and promoting the development of interdisciplinary treatment strategies.