Thyroid Hormone and Cardiovascular Health

Thyroid hormone has important effects on heart muscle, blood circulation, and the central nervous system – all of which are vital for cardiovascular health. This suggests that thyroid hormone levels may help predict heart health. There is growing body of evidence that supports the beneficial effects of thyroid hormone on various cardiovascular markers:
1. Thyroid hormone helps the heart pump more blood efficiently. [150]
2. Thyroid hormone improves cardiovascular health by increasing heart rate. [151-154]
3. Thyroid hormone improves blood circulation within the heart by increasing red blood cell production, total blood volume, and heart contractility. [155-157]
4. Thyroid hormones also increase venous return, resulting in greater cardiac output and blood volume distributed in different body parts. [158-160]
5. A deficiency in thyroid hormone compromises the function of the heart muscle, resulting in lower heart rate and weakening of myocardial contraction and relaxation. [161-162]
6. Thyroid hormone deficiency also leads to lower total blood volume pumped by the heart muscle. [163-164]
7. Low free T3 levels inhibit formation of new blood vessels in the heart tissue after a heart attack, which would accelerate heart failure and adverse cardiac events. [165-166]
8. Thyroid hormone deficiency is also associated with abnormal heart rhythm. [167-168]
9. In people with thyroid hormone deficiency, their risk of developing atherosclerosis (plaque formation), coronary heart disease, and heart failure is significantly increased. [169-171]
10. T3 and T4 administration in patients with primary hypothyroidism lower risk of cardiovascular disease by improving lipid profile and body weight. [172-181]
11. Patients with increased thyroid hormones have increased contractile force and cardiac output. [182-187]
12. Patients with thyroid dysfunction have reduced exercise tolerance compared to those with healthy thyroid hormone levels. [188]
13. Evidence obtained from cell and animal models suggest that thyroid hormone treatments promote regeneration of the damaged heart muscle. [189-196]
14. Thyroid hormone also helps maintain cardiac cell shape and growth. [197-199]
15. Thyroid hormone protects against ischemic heart (lack of oxygen) by accelerating heart rhythm and increasing contractility. [200-201]
16. In patients with thyroid hormone deficiency and heart disease, thyroid hormone therapy normalizes heart function and other cardiovascular parameters. [202-204]
17. In patients with cardiomyopathy (disease of the heart muscle), T4 treatment induces significant improvement in cardiac pump function and functional capacity during exercise. [205-206]
18. In patients with advanced heart failure and low T3 levels, higher dose of T3 improves cardiac output significantly by reducing systemic vascular resistance (resistance that must be overcome to efficiently pump blood through the circulatory system). [207-210]