Studies on the relationship between thyroid stimulating hormone (TSH) within the 
reference range and coronary artery disease (CAD) have produced conflicting 
results. Furthermore, the effect of age on this relationship has never been 
explored. The aim of this study was to investigate the association between TSH 
levels and CAD among euthyroid subjects and whether age influenced this 
relationship. A total of 318 subjects who underwent coronary angiography were 
included. Serum TSH, T3, T4, lipid, blood glucose and creatinine levels were 
measured and compared between the groups with and without CAD. Age-stratified 
analysis and multivariate logistic regression analysis were performed. Levels of 
TSH, T3 and T4 did not differ significantly between CAD (n=196) and non-CAD 
group (n=122) (TSH: 1.77 ± 0.99 vs 1.89 ± 0.98 mIU/L, T3: 1.45 ± 0.36 vs 1.51 ± 
0.35 nmol/L, T4: 100.06 ± 20.49 vs 103.95 ± 24.06 nmol/L, respectively) when 
comparisons were performed among all subjects. A significant between-group 
difference in levels of TSH was observed among subjects less than or equal to 65 
years old (CAD group: n=121, non-CAD group: n=106), with higher TSH levels in 
CAD group (2.03 ± 0.94 vs 1.75 ± 0.97 mIU/L, adjusted p=0.024). Multivariate 
logistic regression analysis revealed that elevated level of TSH was an 
independent predictor for CAD (odds ratio: 1.512, p=0.011). No significant 
between-group difference in TSH levels was observed among subjects older than 65 
years (CAD group: n=75, non-CAD group: n=16). The results showed that higher 
levels of TSH within the reference range were independently associated with the 
presence of CAD only among subjects less than or equal to 65 years old, 
suggesting age might influence the relationship.