The oxidative balance score impacts serum FT4 levels and all-cause mortality in Euthyroid Participants

Abnormal fluctuations in thyroid function within the reference range were strongly associated with increased all-cause mortality. This study aimed to analyze the association between oxidative balance score (OBS) and biomarkers of thyroid function in euthyroid adults and to further investigate whether oxidative balance status affects all-cause mortality by regulating these biomarkers. 5727 euthyroid adults were selected from the National Health and Nutrition Examination Survey (NHANES). Weighted linear regression investigated the potential association of OBS with free thyroxine (FT4) and thyrotropin (TSH). In addition, COX proportional hazard models and restricted cubic spline (RCS) were used to investigate the association between OBS, FT4, TSH, and all-cause mortality. Mediating analyses were performed to determine whether FT4 and TSH modulated the relationship between OBS and all-cause mortality. The results showed that OBS was negatively correlated with FT4 concentration in euthyroid adults. In addition, OBS and FT4 were significantly associated with all-cause mortality. Mediation analysis showed that serum FT4 level mediated the relationship between OBS and FT4 to a certain extent. Among euthyroid individuals, antioxidant OBS significantly correlates with lower FT4 levels. Adherence to an antioxidant diet and lifestyle may help maintain healthier serum FT4 levels, significantly reducing the risk of all-cause mortality.