The relationship between serum thyroid hormone levels, subclinical hypothyroidism, and coronary collateral circulation in patients with stable coronary artery disease

OBJECTIVE
Thyroid disease is a common endocrine disease with important effects on the cardiovascular system. As an adaptive response to myocardial ischemia, coronary collateral circulation (CCC) plays an important role in obstructive coronary artery disease (CAD). The association between serum thyroid hormone levels and development of CCC was investigated in the present study.

METHODS
In total, 430 consecutive patients who underwent coronary angiography procedure and had documented total occlusion in at least 1 major coronary artery were investigated retrospectively. Degree of CCC was classified according to Cohen-Rentrop method. Serum free triiodothyronine (FT3), free thyroxine (FT4) and thyroid-stimulating hormone (TSH) were assessed by the chemiluminescence immunoassay technique.

RESULTS
In spite of diabetes mellitus (p=0.019), smoking (p<0.001), and TSH (p<0.001), FT3 (p<0.001), FT4 (p=0.015), and subclinical hypothyroidism (SCH) (p<0.001) ratios were significantly different between groups. In regression analysis, SCH (p=0.024), DM (p=0.021), smoking (p<0.001), and heart failure (p=0.029) were independent predictors of poor CCC development in multivariate model 1. When regression analyses were performed based on multivariate model 2, TSH (p<0.001), FT3 (p<0.001), heart failure (p=0.022), smoking (p<0.001), and hyperlipidemia (HPL) (p=0.046) were independent predictors of poor CCC development.

CONCLUSION
In addition to traditional risk factors, SCH, higher serum TSH, and lower FT3 levels were associated with development of poor CCC in patients with obstructive CAD.