Influence of medication for lifestyle diseases on thyroid function during health examinations

Introduction Various drugs reportedly influence thyroid function. Lifestyle diseases such as diabetes, dyslipidemia, and hypertension are prevalent worldwide, and patients often take medications for these conditions. However, the relationship between these drugs and thyroid function, especially in the general population, remains incompletely understood. Methods This study aimed to investigate the independent effects of medications for lifestyle diseases on thyroid function through a retrospective cohort study of medical checkup participants who visited the Enshu Hospital between April 2010 and December 2020 (n = 2,814). The clinical history as well as concurrent measurements including TSH, free thyroxine (FT4), and estimated glomerular filtration rate were reviewed to consider various confounding factors influencing thyroid function in individuals. Results When factors influencing FT4 levels were assessed through simple and multiple linear regression analyses, sulfonylureas (β = 0.041, p = 0.030), α-glucosidase inhibitors (β = 0.039, p = 0.036), and thiazolidinediones (β = 0.053, p = 0.004) emerged as independent predictors of elevated FT4 levels. Subsequent analyses, including unpaired t-tests after analysis of covariance adjusted for propensity scores, confirmed the association for thiazolidinediones (15.7 vs. 17.2 pmol/L, p = 0.027). Investigating the factors influencing thyroid-stimulating hormone levels revealed no significant predictors among various medications. Conclusions Sulfonylureas, α-glucosidase inhibitors, and thiazolidinediones independently contribute to elevated serum FT4 levels. While the clinical relevance might be limited, it is essential for phisicians to consider these medications, especially thiazolidinediones, when interpreting thyroid function testing.