Thyroid Cancer's Connection to Cardiovascular Disease

The cancer, and its treatments, can pose a risk to your heart health

heart disease, thyroid cancer, tsh suppression, levothyroxine
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Cardiovascular (CV) disease—encompassing heart disease, stroke, aortic aneurysms, and other concerns—is one of the long-term consequences of thyroid cancer. There are several contributing factors for this association, both related to the disease itself and its treatments. Unfortunately, even when thyroid cancer is treated adequately, CV disease can develop.

What Poses Risk to Your Cardiovascular Health

There are several reasons for the association between thyroid cancer and CV disease. Thyroid cancer can produce a number of physical effects, some of which directly contribute to the development of cardiovascular issues.

Several of the therapeutic methods used for the treatment of thyroid cancer also contribute to the development of CV disease.

Hyperthyroidism

While it is not always the case, thyroid cancer can manifest with an overactive thyroid gland, which produces excessive thyroid hormones. The effect is hyperthyroidism, which can have several consequences, several of which are related to cardiovascular health:

  • Hypertension (high blood pressure) is a known risk factor for angina (chest pain), heart attacks, and ischemic stroke, and it's the leading cause of cardiovascular disease. Thyroid cancer increases the lifelong risk of developing hypertension, even after treatment. Hyperthyroidism is believed to be partially responsible for this link; chemotherapeutic medications, which are used for cancer treatment, contribute as well.
  • Atrial fibrillation is an irregular heart rhythm that can lead to the formation of blood clots that travel throughout the body, resulting in heart attacks, strokes, or blood clots in the lungs, intestines, legs, or arms. The risk of atrial fibrillation is associated with hyperthyroidism, and this risk is sharply increased with thyroid cancer for unknown reasons.

Levothyroxine Suppression

After surgical removal of the thyroid gland and, in some cases, after treatment with radioactive iodine, you may be given a prescription for a high dose of levothyroxine. This medication is a thyroid hormone replacement, and high doses (known as supra-physiologic doses) are used to suppress the thyroid stimulating hormone (TSH) level. Keeping very low or undetectable TSH levels can prevent recurrence of the thyroid cancer.

However, the use of supraphysiologic doses of levothyroxine is also strongly associated with an increased risk of CV disease and atrial fibrillation.

Thyroidectomy

Removing thyroid cancer by completely resecting the thyroid gland is associated with a lower chance of cancer recurrence, but a higher risk of CV disease. It is believed that thyroid resection may stimulate hormones that cause CV disease.

Radioactive Iodine

Used for treatment of thyroid cancer, radioactive iodine binds to and destroys cancerous thyroid tissue, as well as normal tissue in the thyroid gland. Treatment with radioactive iodine has been linked with a high occurrence of CV disease after thyroid cancer, though the reasons why are not clear.

The additive effects of thyroid cancer and its treatment mean that CV disease is a real concern if you have or have had thyroid cancer.

Managing Your Cardiovascular Disease Risk When You Have Thyroid Cancer

If you have or have had thyroid cancer, it is important to understand that adequate cancer treatment does not mean that you no longer have to deal with some of the complications of cancer.

While it can be upsetting to know that your cancer effects have not truly disappeared after treatment of the tumor, CV disease risk factors can be effectively managed.

Be sure to maintain regular medical visits with your doctor, as yearly physicals routinely include measurements of your blood pressure and assessments of your heart rhythm (which can help your doctor detect atrial fibrillation). That said, don't hesitate to make an earlier appointment if you are experiencing any symptoms you are concerned about.

If you have signs of heart disease or hypertension, your doctor may prescribe medication to regulate your heart rhythm, optimize your blood pressure, or reduce your risk of developing a blood clot.

A Word From Verywell

If you have or have had thyroid cancer, you should know that there are several types of thyroid cancer, and the prognosis varies depending on which type you have. As you are dealing with treatment for your cancer, you also need to be attentive to how your cancer and your thyroid function can affect your health. With attention, effects of thyroid cancer and thyroid disease can be managed to reduce the impact of your condition on your overall health.

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