Thyroid hormone has many effects on the heart and cardiovascular system. 
Thyrotoxicosis is associated with increased cardiovascular morbidity and 
mortality, primarily due to heart failure and thromboembolism. However, the 
relationship between thyroid hormone excess and the cardiac complications of 
angina pectoris and myocardial infarction remains largely speculative. Moreover, 
few studies have been reported on the effect of thyroid hormone levels within 
normal range on coronary artery disease (CAD). Therefore we examined the 
association of thyroid function with coronary artery diseases in euthyroid 
angina patients. Total 192 subjects (mean age; 60.8 yrs) were enrolled in which 
coronary angiograms were performed due to chest pain. We measured free thyroxine 
(FT(4)), thyroid stimulating hormone (TSH), serum lipid levels and 
high-sensitivity C-reactive protein (hsCRP) levels and analyzed their 
association with the presence of CAD. Serum FT(4) levels were higher in patients 
with CAD compared with the patients without CAD (1.31 +/- 0.30 vs 1.20 +/- 0.23, 
p = 0.006), and high FT(4) level was associated with the presence of 
multi-vessel disease. Multivariate analysis showed that age (odds ratio (OR) 
1.04; 95% confidence interval (CI) 1.01-1.07, p = 0.007), hypertension (OR 2.04; 
95% CI 1.06-3.90, p = 0.036) and FT(4) (OR 4.23; 95% CI 1.12-15.99, p = 0.033), 
were the determinants for CAD. The relative risk (RR) for CAD in highest tertile 
of FT(4) showed increased risk compared with the lowest tertile (RR 1.98; 95% CI 
0.98-3.99, p<0.001). Our study showed that FT(4) levels were associated with the 
presence and the severity of CAD. Also, this study suggests that elevated serum 
FT(4) levels even within normal range could be a risk factor for CAD. Further 
studies will be necessary to confirm the relationship of thyroid function and 
CAD.