Response by Bano et al to Letter Regarding Article, "Thyroid Function and the Risk of Atherosclerotic Cardiovascular Morbidity and Mortality: The Rotterdam Study".

RATIONALE Thyroid hormones have been linked with various proatherogenic and antiatherogenic processes. However, the relationship of thyroid function with manifestations of atherosclerosis remains unclear. OBJECTIVE To investigate the association of thyroid function with atherosclerosis throughout its spectrum; that is, subclinical atherosclerosis, incident atherosclerotic cardiovascular (ASCV) events, and ASCV mortality. METHODS AND RESULTS This population-based study was embedded within the Rotterdam Study. The risk of atherosclerosis was evaluated by measuring (1) presence of subclinical atherosclerosis, assessed by coronary artery calcification score >100 AU; (2) ASCV events, defined as fatal and nonfatal myocardial infarction, other coronary heart disease mortality, or stroke; (3) ASCV mortality, defined as death because of coronary heart disease and cerebrovascular or other atherosclerotic diseases. Associations of thyroid-stimulating hormone and free thyroxine with the outcomes were assessed through logistic regression and Cox proportional hazard models, adjusted for potential confounders, including cardiovascular risk factors. A total of 9420 community-dwelling participants (mean age±SD, 64.8±9.7 years) were included. During a median follow-up of 8.8 years (interquartile range, 4.5-11.8 years), 934 incident ASCV events and 612 ASCV deaths occurred. Free thyroxine levels were positively associated with high coronary artery calcification score (odds ratio, 2.28; 95% confidence interval, 1.30-4.02) and incident ASCV events (hazard ratio, 1.87; confidence interval, 1.34-2.59). The risk of ASCV mortality increased in a linear manner with higher free thyroxine levels (hazard ratio, 2.41; confidence interval, 1.68-3.47 per 1 ng/dL) and lower thyroid-stimulating hormone levels (hazard ratio, 0.92; confidence interval, 0.84-1.00 per 1 logTSH). Results remained similar or became stronger among euthyroid participants. CONCLUSIONS Free thyroxine levels in middle-aged and elderly subjects were positively associated with atherosclerosis throughout the whole disease spectrum, independent of cardiovascular risk factors.