Association of serum thyrotropin levels with coronary artery disease documented by quantitative coronary angiography: a transversal study

Abstract

Objective: The association between coronary artery disease (CAD) and thyroid function remains controversial. We evaluated the thyroid function and graduated well-defined CAD as confirmed by quantitative coronary angiography (CA).

Subjects and methods: We evaluated the serum TSH, free thyroxine, free triiodothyronine and thyroid antibody levels in 300 consecutive patients (age 61.6 ± 9.9 years and 54% were male) undergoing CAD diagnosis as confirmed by CA. Plaques with ≥ 50% stenosis being indicative of obstructive CAD, and patients were divided into groups according to main epicardial coronary arteries with plaques (0, 1, 2, 3). Lipid profiles and a homeostasis model assessment (HOMA-IR) were determined.

Results: Serum median (25% and 75% percentile) TSH levels in patients with group 2 and 3 (2.25; 1.66-3.12 mU/L and 4.99; 4.38-23.60 mU/L, respectively) had significantly higher TSH concentrations (p < 0.0001) than the group 0 (1.82; 1.35-2.51 mU/L). Furthermore, patients of group 3 had higher TSH concentration (p < 0.0001) than those of group 1 (1.60; 0.89-2.68 mU/L). Group 3 were older (64 ± 8.5 vs. 59 ± 9.5, p = 0.001), had more patients with dyslipidemia (84% versus 58%, p < 0.001), male (54% versus 44%, p = 0.01), hypertension (100% versus 86%, p < 0.001), and smoking (61% versus 33%, p < 0.001) than group 0. Multivariate stepwise logistic analysis showed TSH, age, HbA1c, and HOMA-IR were the CAD associated variables.

Conclusions: In this cohort, elevated TSH levels in the high normal range or above are associated with the presence and severity of CAD besides may represent a weak CAD risk factor.

Figure 1. Box- and-whisker plot of the differences in the serum TSH median observed between patients undergoing the coronary angiography. Group 0; absence of coronary artery disease (when the vessels were < 50% of the internal diameter). Group 1, 2, and 3; according to the number of vessels with significant stenosis. The median is the center line, the ends of the box represent the 25^th and 75^th percentiles, and the ends of the lines extend to the 2.5^th and 97.5^th percentiles.

Differences between the groups were analyzed by the Kruskal-Wallis test. (H = 203.5; p < 0.0001). ^a p < 0.02 vs. group 0; ^b p < 0.0001 vs. group 0, 1 and 2 (Verified by the Mann-Whitney test was used).