Thyroid Hormone vs. Heart Disease and Metabolic Syndrome

The aim of this prospective study was to assess the role of thyroid hormones in the prognosis of patients with heart disease?. Conclusions: Low-T3 syndrome is a strong predictor of death in cardiac patients and might be directly implicated in the poor prognosis of cardiac patients.

Iervasi G et al. Low-T3 syndrome: a strong prognostic predictor of death in patients with heart disease. Circulation 2003 Feb 11;107(5):708-13.

We have demonstrated that carotid intima-media thickness is independently associated with thyroid function within the normal reference range, which suggests an increased cardiovascular risk in subjects with low-normal thyroid function.

Thyroid function is associated with carotid intima-media thickness in euthyroid subjects. Atherosclerosis 2009; 204:77-81.

1149 women participated in a large study of chronic disease in older persons in Rotterdam, the Netherlands. All of the women in the study had been through menopause. Between 1990 and 1993, the researchers evaluated women in the study to see if they had blockages in their aorta (a large blood vessel leading from the heart to the body) or any evidence of a past heart attack. At the same time, the researchers collected blood tests of thyroid function.

RESULTS: Women with subclinical hypothyroidism (meaning T4 levels within “normal” range, but elevated TSH) were almost twice as likely as women without this condition to have blockages in the aorta. They were also twice as likely to have had heart attacks.

Subclinical Hypothyroidism Is an Independent Risk Factor for Atherosclerosis and Myocardial Infarction in Elderly Women: The Rotterdam Study. Ann Intern Med February 15, 2000 132:270-278

We found that TSH levels were associated with Metabolic syndrome in euthyroid postmenopausal women, independently of well known Metabolic Syndrome risk factors. LDL cholesterol and triglycerides were independently associated with TSH levels.

Subjects with high-normal TSH levels had a 1.95-fold increased risk of metabolic syndrome as compared to those with low-normal TSH levels.

Thyroid stimulating hormone is associated with metabolic syndrome in euthyroid postmenopausal women.

Maturitas 2009; 62:301-305

Thyroid hormone metabolism is frequently altered in patients with heart disease, leading to a fall in T3 levels potentially resulting in cellular hypothyroidism within the myocardium? Low serum T3 may contribute to contractile dysfunction.

Thyroid Hormone Therapy of Cardiovascular Disease. CVR&R. 2002;23:20-26

Decreased Free T3 levels? were associated with worse NYHA [New York Heart Association heart failure] class. ?Patients with ventricular tachycardia demonstrated significantly lower serum values of Free T3.

Shimoyama N et al. [Serum thyroid hormone levels correlate with cardiac function and ventricular tachyarrhythmia in patients with chronic heart failure]. J Cardiol 1993;23(2):205-13.

In our study, we found significant associations between low levels of Free T3, poor performance, and increased mortality.

Thyroid Status in Old Age. JAMA 2004 Vol 292, No. 21

Evidence of an association between subclinical hypothyroidism and cardiovascular disease is mounting. The impact of thyroid hormone on lipid levels is mediated primarily through T3. Thus the decreased T3 seen in hypothyroidism may result in increased serum cholesterol.

An Association Between Varying Degrees of Hypothyroidism and Hypercholesterolemia in Women: The Thyroid-Cholesterol Connection. Preventive Cardiology, Vol. 4, Issue 4, pp 179-182, Fall 2001