The Role of the Parametric Thyroid Feedback Quantile Index in Cardiovascular Risk Evaluation Among Euthyroid Koreans

Abstract Context Thyroid hormones play a crucial role in metabolic regulation and maintaining cardiovascular homeostasis. The Parametric Thyroid Feedback Quantile-based Index (PTFQI) assesses central thyroid hormone sensitivity by standardizing the inverse relationship between free thyroxine (T4) and thyroid-stimulating hormone (TSH). Objective To investigate the relationship between PTFQI and cardiovascular risk in the euthyroid Korean population. Methods Using data from the 2013-2015 Korea National Health and Nutrition Examination Survey, we included 5,160 euthyroid adults aged 18 to 80 who were not previously diagnosed with cardiovascular or thyroid disease. Cardiovascular risk was evaluated using the PREVENT (Predicting Risk of cardiovascular disease EVENTs) and PCE (Pooled Cohort Equations) scores. Results Stratification by PTFQI quartiles revealed an inverse relationship between PTFQI and cardiovascular risk. Higher PTFQI quartiles were associated with lower risks of cardiovascular disease (adjusted odds ratio [aOR], –0.55; 95% confidence interval [CI], –0.92 to –0.18), atherosclerotic cardiovascular disease (aOR, –0.31; 95% CI –0.53 to –0.08), heart failure (aOR, –0.26; 95% CI –0.47 to –0.05), coronary heart disease (aOR, –0.15; 95% CI -0.28 to –0.02), and ischemic stroke (aOR, –0.18; 95% CI –0.30 to –0.06). These associations persisted after adjusting for thyroid peroxidase antibodies, iodine intake, alcohol consumption, physical activity, and income level. The PCE score demonstrated a strong correlation with the PREVENT score. Conclusion The PTFQI inversely correlated with cardiovascular risk among euthyroid Koreans, indicating that reduced central sensitivity to thyroid hormone is associated with lower cardiovascular risk. These results underscore the importance of considering population-specific thyroid function parameters in cardiovascular risk assessment.