Aim

To prospectively investigate the association of individual thyroid function and sensitivity with cardiovascular and all-cause mortality in adult euthyroid patients with metabolic dysfunction-associated steatotic liver disease (MASLD).

Material and methods

Data for the study came from 1198 MASLD participants with normal thyroid function in the National Health and Nutrition Examination Survey (NHANES 2007-2012). The Thyroid-Stimulating Hormone Index (TSHI), Thyrotroph T4 Resistance Index (TT4RI), and Thyroid Feedback Quantile-based Index (TFQIFT4) were used to assess thyroid hormone sensitivity. Kaplan-Meier survival curves, Cox proportional hazard regression models, restricted cubic splines, subgroup analyses, and a series of sensitivity analyses were used to explore the association of thyroid function and thyroid hormone sensitivity with cardiovascular and all-cause mortality.

Results

During a median follow-up of 11.1 years (12,188.8 person-years), 178 (14.9%) all-cause deaths were recorded, of which 46 (3.8%) were cardiovascular deaths. After adjusting for multiple factors, such as demographic characteristics, lifestyle, economic and social factors, and blood indices, free thyroxine (FT4) was independently correlated with all-cause mortality, and the risk of all-cause mortality increased by 16.2% for each unit increase in FT4 (95% CI: 1.044-1.293). For every one-unit increase in FT4, the risk of all-cause death was increased by 35.3% (95% CI: 1.168-1.567). Furthermore, when stratified by age, sex, race, body mass index (BMI), hypertension, and diabetes, the results were not uniformly significant.

Conclusions

In MASLD patients with normal thyroid hormones, higher FT4 levels were significantly associated with increased risk of all-cause mortality, while higher FT4 levels were significantly linearly associated with cardiovascular mortality.