How does thyroid disease affect the heart?

One of the most important reasons for diagnosing and treating thyroid disease is to prevent heart disease that can result.

Thyroid disease can exacerbate heart symptoms in people with heart disease and accelerate underlying heart problems. It can even create new heart problems in people with healthy hearts.

This article explains the role of the thyroid and how it affects the heart. It also covers the differences in symptoms and treatment between underactive and overactive thyroid.


By producing the right amount of thyroid hormone, the thyroid helps regulate your body’s metabolism — most importantly, how much oxygen and energy your body uses — as well as your digestive function, muscle function, and skin tone.

The thyroid has at least some effect on every organ in the body, including the heart.

Too little thyroid hormone (called hypothyroidism) or too much thyroid hormone (called hyperthyroidism) can affect the heart in different ways.

Anatomy of the Thyroid


Hypothyroidism, known as an underactive thyroid, can be a subtle disorder. It usually starts gradually, so its symptoms can easily lurk in someone.

Additionally, hypothyroidism often occurs without typical “textbook” symptoms, especially in older adults.

When thyroid hormones are insufficient, neither the heart nor blood vessels work properly.

Decreased thyroid hormone levels cause the heart muscle to pump less and eventually become weak.

Also, the heart muscle does not fully relax after each heartbeat. This failure to relax can lead to diastolic dysfunction or a stiffening of the heart’s pumping chambers — a condition that can lead to heart failure.

Hypothyroidism can also cause blood vessels to harden, which can lead to high blood pressure (hypertension).

If you have any symptoms of hypothyroidism that your healthcare provider cannot explain, such as fatigue or weight gain, have them measure your thyroid hormone levels. This is especially important if you already have heart disease.

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heart symptoms

Heart symptoms can occur in anyone with hypothyroidism, but are especially likely to occur in people who already have underlying heart disease.

Common heart problems associated with hypothyroidism include:

  • Swelling (edema): Edema may be the result of worsening heart failure.In addition, hypothyroidism itself produces a type of edema called myxedemawhich is caused by the accumulation of abnormal proteins and other molecules in the fluid surrounding the body’s cells.
  • Arrhythmias: Hypothyroidism may also exacerbate a tendency to premature beats and irregular, shaking heartbeats (atrial fibrillation).
  • Heart failure (new or worsening): Hypothyroidism can lead to heart failure for the first time in patients with relatively mild underlying heart disease.
  • High diastolic blood pressure (diastolic hypertension): Arteries can become stiff due to hypothyroidism, leading to increased diastolic blood pressure.
  • Shortness of breath (dyspnea): Shortness of breath on exertion and poor exercise tolerance in hypothyroidism are usually due to skeletal muscle weakness. In people who also have heart disease, this may be due to worsening heart failure.
  • Slow heart rate (bradycardia): Your heart rate is regulated by thyroid hormones. The heart rate of people with hypothyroidism is usually 10 to 20 beats per minute slower than normal, especially those with heart disease.
  • Worsening of coronary artery disease (CAD): A reduction in thyroid hormones can actually reduce the frequency of angina (chest discomfort associated with CAD). However, the increases in LDL cholesterol (“bad cholesterol”) and C-reactive protein (an inflammatory protein) that occur in hypothyroidism may accelerate any underlying CAD.

The link between thyroid disease and cholesterol

Hypothyroidism Treatment

Doctors often prescribe Synthroid (levothyroxine) to treat an underactive thyroid.

Taken once a day, this replacement hormone mimics thyroxine, the hormone naturally produced by the thyroid.

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If you start taking thyroid medication, expect to take it for the rest of your life. The effects of hypothyroidism are irreversible.

Medications that can be used to treat thyroid disease


Hyperthyroidism is caused by excessive secretion of thyroid hormones. When there is too much thyroid hormone, the heart muscle has to work harder. For people with heart disease, an overactive thyroid can cause a lot of physical damage.

Excessive thyroid hormone increases the contractility of the heart muscle and increases the amount of oxygen the heart needs. It also increases heart rate. As a result, the work of the heart is greatly increased.

Like hypothyroidism, hyperthyroidism may not produce classic textbook symptoms. Therefore, if you have heart symptoms that cannot be easily explained otherwise, measure your thyroid function. The sooner the better.


heart symptoms

Heart symptoms can occur in anyone with hyperthyroidism, but are especially dangerous for those with underlying heart disease.

Common symptoms include:

  • fast heart rate (Tachycardia) and palpitations: Undetected hyperthyroidism is a common cause of increased heart rate at rest and with mild exertion. Hyperthyroidism should always be ruled out with blood tests before diagnosing inappropriate sinus tachycardia.
  • Arrhythmias: Especially in patients with underlying heart disease, hyperthyroidism can also produce many other cardiac arrhythmias, such as premature ventricular contractions (PVCs), ventricular tachycardia, and especially atrial fibrillation.
  • Heart failure: Hyperthyroidism itself can lead to heart failure, but it is rare. On the other hand, it is common for hyperthyroidism to lead to a greater risk of heart failure if there is pre-existing heart disease. This can be difficult to treat.
  • High systolic blood pressure (systolic hypertension): Strong heart contractions increase systolic blood pressure, or the pressure within the blood vessels during systole.
  • Shortness of breath: Shortness of breath on exertion may be due to skeletal muscle weakness or worsening heart failure associated with hyperthyroidism.
  • Worsening angina: Hyperthyroidism symptoms often worsen in people with coronary artery disease. These can include increased angina or even a heart attack.
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Hyperthyroidism can cause your heart rate to increase at rest.

Hyperthyroidism Treatment

Doctors often prescribe stazol (methimazole) or propylthiouracil (PTU) to treat hyperthyroidism. It’s important to remember that these treatments are not cures.

If tablet treatment is unsuccessful, surgery to remove all or part of the thyroid may be an option. The same goes for radioactive iodine therapy to slow the production of thyroid hormones.

Three Ways to Treat an Overactive Thyroid


The thyroid is a small butterfly-shaped gland in the back of the throat that has many important functions. As a result, thyroid disease — which causes too little (hypothyroidism) or too much (hyperthyroidism) thyroid hormones — can have a variety of consequences.

Heart problems top the list. among them? Increased blood pressure, irregular heartbeat, slow or fast heart rate, heart failure, etc.

Managing thyroid disease has more benefits than just reducing symptoms like fatigue. This includes reducing your risk of some of these problems. If you have any signs, or if you have a new or worsening heart health problem, be sure to get tested for thyroid disease.

Frequently Asked Questions

  • Who is most at risk for thyroid problems?

    You are more likely to develop thyroid disease if you are female, white, 60 years or older, have a family history of thyroid disease, or have diabetes, rheumatoid arthritis, or radiation therapy.

  • How to prevent thyroid disease?

    To reduce your risk, ask for a thyroid collar before taking an x-ray, quit smoking, self-examine your neck for lumps and swelling, limit your soy intake, consider selenium dietary supplements, and see your doctor regularly.