Effect of age on the association between normal thyroid hormone level and coronary artery disease

Abstract

Objective To investigate the effect of age on the association between normal thyroid hormone level and coronary artery disease (CAD). Methods A total of 1163 euthyroid patients undergoing coronary angiography (CAG) from January 2013 to June 2014 were enrolled and categorized into 2 groups: the young and middle-aged group (<60 years, n=602) and the elderly group (≥60 years, n=561), and each group was sub-grouped into the CAD and non-CAD group according to CAG. Height, body weight, and levels of serum lipid, fasting blood glucose, glycosylated hemoglobin, free triiodothyronine (FT3), free thyroxine (FT4) and thyroid-stimulating hormone (TSH) were measured. Results In the youth and middle-aged group, 309 patients (51.3%) were diagnosed as CAD, and there was no significant difference in the levels of FT3, FT4 and TSH between CAD and non-CAD patients 〔(5.3±0.6)mmol/L vs. (5.3±0.5)mmol/L, (11.8±1.9)mmol/L vs. (11.8±1.8) mmol/L, (2.0±1.1) mIU/L vs. (2.0±1.0)mIU/L, all P>0.05〕. In the elderly group, 357 patients (63.6%) were diagnosed as CAD, and the FT3 level was lower in the CAD patients than in the non-CAD patients〔(5.1±0.6)mmol/L vs. (5.2±0.5)mmol/L, P<0.01〕. Logistic regression demonstrated that FT3 was an independent influencing factor for CAD in elderly patients (OR=0.564, P<0.01). Conclusions The association between normal thyroid hormones levels and CAD varies along with age. Thyroid hormones have no relationships with CAD in the young and middle-aged people. The decline of FT3 level may increase the risk of CAD in the elderly. Key words: Thyroid hormones; Coronary disease; Age factor