Normal thyroid function and its relationship with carotid artery stenosis in patients with coronary artery disease

This study was carried out to determine the relationship between normal ranges of thyroid function and internal carotid artery stenosis (ICS) in patients with coronary artery disease (CAD). 100 euthyroid patients with concomitant ICS and CAD (group 1) were analyzed retrospectively. Comparison was made with 100 euthyroid patients with CAD who were free of any carotid artery lesions (group 2). Normal ranges of FT4 were classified into 3 groups: low-normal, mid-normal, and high-normal thyroid groups. Mean FT4 level in group 1 was significantly higher than group 2 (p=0.02). Percentage of patients in high-normal FT4 group was significantly higher in group 1 than in group 2 (p< 0.001). According to the categories of FT4, the percentage of patients with ICS in the high- normal FT4 group (76.1%) was significantly higher than low-normal (39.4%) and mid-normal group (43%) (p=0.003 and p<0.001 respectively). Logistic regression analysis showed that high-normal FT4 group was independently associated with ICS (OR 4, 95% CI 1.84-8.77, p<0.001). Increased FT4 levels, even within the reference range was associated with a higher percentage of ICS in euthyroid patients with CAD, independent of classical risk factors for atherosclerosis.