Features April 2011 Issue

Treat Thyroid Disease to Help Protect Your Heart

Thyroid disease can sometimes cause heart palpitations, but even worse it can increase your risk of atrial fibrillation.

If you have some form of heart disease and your condition worsens, be sure that your thyroid function is checked regularly, as it may be contributing to your problems. The thyroidís function is to absorb iodine, an element found mainly in salt, bread, and fish, and convert it into thyroid hormones: thyroxine (T4) and triiodothyronine (T3). These hormones control the bodyís metabolism, which controls the function of your heart, brain, skin, and digestive system. This means that if your thyroid isnít doing its job properly it can affect almost every aspect of your health.

"Thyroid hormone is very important for normal cardiovascular function, such as normal blood pumping function of the heart, normal heart rate, regulating normal blood pressure control, and regulating blood cholesterol levels," says Betul A. Hatipoglu, a staff member in the Department of Endocrinology, Diabetes and Metabolism at Cleveland Clinic. "For patients with heart disease, thyroid hormone abnormalities can worsen the underlying heart problem or cause new problems."

Causes of Thyroid Disease

Thyroid disorders are triggered by a range of factors. Autoimmune diseases, such as Hashi­motoís thyroiditis, are a common cause. Autoimmune diseases occur when the immune system mistakenly attacks the bodyís own tissues.

Hyper­thy­roidism in older adults is most likely related to thyroid nodules, abnormal growths that form in the gland. Most donít cause signs or symptoms unless they grow to a large size, when they may produce more T4 and T3, resulting in hyperthyroidism. In older adults, an overactive thyroid may also be due to Gravesí disease, an autoimmune disease similar to Hashimotoís. It stimulates the thyroid to secrete more hormones, speeding up metabolism.

Medications also can affect thyroid function. For example, the drug amiodarone (Corderone, Pacerone), which is used to treat heart arrhythmias, can induce both an overactive and underactive thyroid, particularly in patients with existing thyroid problems. Some biological therapies used to treat cancer, including sunitinib (Sutent) and imatinib (Gleevec), also may cause or worsen an underactive thyroid.

Hypothyroidism Versus Hyperthyroidism

Studies suggest that the classic symptoms of hyperthyroidism (see chart) are less common in older adults, and that these patients are more likely to present with no symptoms at all. This is referred to as apathetic hyperthyroidism and can be difficult to diagnose.

"In hyperthyroidism (when too much hormone is present), a fast heart beat or irregular heartbeats with arrhythmias could be a problem," says Dr. Hatipoglu. "It can also result in heart failure, hypertension, and if patient already has coronary artery disease, hyperthyroidism could exacerbate the problem and result in heart attack or stroke."

Hypothyroidism (when not enough hormone is present) can cause left-sided heart failure, a potentially life-threatening condition. According to Dr. Hatipoglu, "In hypothyroidism the heart muscle is weakened. This means that the heart cannot pump enough blood with each heartbeat causing heart failure. Also it can cause low heart rate, hypertension, and elevated cholesterol."

The Importance of Seeking Treatment

"Thyroid patients should make sure their disease is well treated and regularly followed," adds Dr. Hatipoglu. "Once the hypothyroidism or hyperthyroidism is treated and stable, the risk for heart disease should be prevented. If they develop heart disease, they should make sure their doctors are aware of their thyroid disease."

The standard treatment for an under­active thyroid is the synthetic thyroid hormone levothyroxine (Levo­throid, Synthroid). Most patients report feeling less tired within a couple of weeks of starting the medication, and it can help reverse weight gain.

For an overactive thyroid, you may be given an anti-thyroid medication such as methimazole (Tapazole), which blocks the production of thyroid hormone. Another option is radioactive iodine, which is taken orally and destroys the overactive thyroid cells, which can result in hypothyroidism and likely require treatment.