Low Thyrotropin Levels Are Associated With an Increased Risk of Atherosclerotic Cardiovascular Disease in Euthyroid Individuals: The Korea National Health and Nutrition Examination Survey 2013-2015.

Objective: This study aimed to determine whether thyrotropin (thyroid-stimulating hormone [TSH]) levels within the physiologic range influence the risk of atherosclerotic cardiovascular disease (ASCVD) in euthyroid individuals.

Methods: A cross-sectional survey was conducted using data from the Korea National Health and Nutrition Examination Survey (2013-2015). After excluding participants with abnormal thyroid function or a history of thyroid disease or ASCVD, 2,995 euthyroid individuals aged 40-79 years were included. ASCVD risk was estimated using the 2013 and 2018 American College of Cardiology/American Heart Association cardiovascular risk assessments (10-year risk, %).

Results: Participants were divided into tertiles based on TSH concentration. After adjusting for confounding factors, the lowest tertile (T1) exhibited the highest ASCVD risk. This association remained significant in both male and female participants after multiple adjustments. Multiple regression analysis, controlling for confounders, indicated that the odds ratio (OR) for high ASCVD risk in T1 was significantly higher than in T2 among men, while the OR for intermediate ASCVD risk was significantly elevated in T1 compared to T2 among women.

Conclusion: Lower TSH levels within the physiologic range were associated with an increased risk of ASCVD in euthyroid individuals. These findings suggest that even individuals with normal thyroid function but low-normal TSH levels might benefit from interventions to reduce ASCVD risk.