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Thyroid Hormone and Cardiovascular Disease - Hypothyroidism

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Too little thyroid hormone can significantly increase your risk of heart disease. A study presented at the 1997 meeting of the American Thyroid Association showed a strong link between abnormal thyroid function and elevated cholesterol levels. Study participants had higher total cholesterol and higher LDL (bad cholesterol) levels than patients with normal thyroid activity did. Those with hypothyroidism may also have very high triglyceride levels. High cholesterol and high triglyceride levels increase the risk for atherosclerosis (hardening of the arteries) and puts you at a higher risk for stroke and heart attack. These levels usually return to normal with the appropriate thyroid hormone replacement.

Persons with low thyroid have a low incidence of angina and myocardial infarction (heart attack). Hypothyroidism may also cause high blood pressure often associated only with too much thyroid hormone. The prevalence of hypertension may be as high as 21% of those with low thyroid levels. In hypothyroidism there is increased peripheral vascular resistance. The smooth muscles of the blood vessels are contracted forcing the heart to use more force (pressure) to push the blood through smaller openings in the vessels. The result is elevated blood pressure readings. High blood pressure also increases your risk level.

Congestive heart failure (CHF) can develop in cases of prolonged hypothyroidism. The heart becomes enlarged and does not pump effectively. Fluid collects in the lungs causing difficulty breathing. The feet and legs become edematous (swell). The condition was once called "dropsy". In fact, the thyroid hormone metabolism is often abnormal in patients with CHF. Researchers are now looking at treating these patients with T3 to improve their outcomes.

The study presented to the American Thyroid Association also showed that many people may be under treated for hypothyroidism. As many as 40% of those in the study still had abnormal TSH (thyroid stimulating hormone) levels. In his book The Thyroid Solution, Dr. Arem recommends maintaining a TSH level of 0.5-2 for the best control and level of well being. He also recommends testing TSH levels as frequently as every three month initially and at least annually for maintainance.

Control of hypothyroidism is vital to control of cardiovascular risk. Elevated levels of cholesterol and high blood pressure may require additional intervention of medication, diet and exercise to reduce risk.

Sources:

Undertreatment of Thyroid Disease Increasing Cardiovascular Risk

CBS Healthwatch Thyroid Hormone and Cardiovascular Disease

Medscape.com Menopausal Status, Dyslipidaemia and Thyroid function

Arem, R, The Thyroid Solution Ballentine Books, New York, 1999 pp. 46-47, 54-55, 275-276