Relationship between thyroid hormones levels and coronary artery disease in euthyroid individuals

Coronary Artery Disease (CAD) is known as one of the leading causes of death in the world. Therefore, in this study, we aimed to investigate the relationship between blood levels of thyroid hormones in euthyroid individuals and the prevalence as well as severity of CAD.

Individuals who underwent coronary angiography were divided into four groups based on their report: 1) normal coronary arteries (NCA); 2) obstruction in one of the arteries; 3) 2‐vessel coronary artery disease (2VD); and 4) 3‐vessel coronary artery disease (3VD). The relationship between CAD and blood levels of thyroid hormones was investigated using the multivariate regression analysis.

In this study, 528 individuals (mean age 54.5±0.7 years) participated; 68% of them were under the age of 65 years. Free triiodothyronine (FT3) serum level was inversely associated with the presence of 2VD in females [OR=0.325; 95%CI:(0.187-0.702)] and in individuals under the age of 65 years [OR=0.401; 95%CI:(0.184-0.601)]. In addaition, there was no significant association between TSH level and 2VD. FT3 was inversely related to 3VD in females and patients under the age of 65 years. Unlike the other groups, the 3VD group had higher serum levels of TSH compared to the NCA group, and therefore the serum TSH level was directly related to of 3VD in patients under the age of 65 years.

Blood levels of thyroid hormone in euthyroid patients are associated with the occurrence of multi-vessel CAD, which indicates that thyroid hormones are only associated with severe CAD.