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Thyroid disorders and heart conditions: What’s the connection?

Watch for an irregular heartbeat and cardiovascular disease.

thyroid disorders heart conditions connection
Thyroid disorders are often overlooked as potential causes of heart problems, but there is a well-established link.
Image: AlexRaths/Thinkstock

The thyroid is a butterfly-shaped gland in your neck. It produces hormones—thyroxine (T4) and triiodothyronine (T3)—that tell your cells if they need to speed up or slow down. But if the thyroid gland is overactive or underactive, the result is a number of consequences and symptoms, sometimes involving the heart. “The connection to the heart is well established, but thyroid problems are often overlooked as the cause,” says Dr. Giuseppe Barbesino, an endocrinologist at Harvard-affiliated Massachusetts General Hospital.

Thyroid conditions

When the thyroid gland puts out too little hormone, it’s called an underactive thyroid; the medical term is hypothyroidism. It may cause a slow heart rate, a rise in cholesterol, an increase in fluid around the heart, and heart failure.

A precursor to hypothyroidism called subclinical hypothyroidism may cause some changes in the blood fats and blood vessel function that may lead to an increased risk of narrowing of the arteries.

When the thyroid puts out too much hormone, it’s called an overactive thyroid or hyperthyroidism. This causes the heart to beat faster, which can lead to palpitations, or an irregular heartbeat known as atrial fibrillation (afib). “Afib is the most common and dangerous heart risk associated with thyroid disorders,” says Dr. Barbesino.

In afib, the heart’s upper chambers (the atria) quiver instead of pumping steadily. This can lead to blood clots forming in the slow-moving blood. If a clot travels in the blood to the brain, it can cause a stroke. Afib can also cause the heart’s main pumping chambers (the ventricles) to pump too fast. The rapid heartbeat and quivering atria can eventually cause heart failure.


Dr. Barbesino says taking medications such as levothyroxine (Synthroid) to replace missing thyroid hormone may help or even reverse some heart conditions when they’re caused by hypothyroidism or subclinical hypothyroidism.

However, he says it’s very difficult to reverse afib in someone with ongoing hyperthyroidism. Medications such as methimazole (Tapazole) can slow down the action of thyroid hormone, and that may help control afib. But the drugs may have side effects such as itching. A common treatment for hyperthyroidism is to destroy or remove the overactive thyroid tissue. This requires you to take thyroid hormone pills for the rest of your life. In addition to correcting other symptoms, it can reverse afib.

Posted by: Dr.Health

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