Your Heart and Your Thyroid: The Connection

Patient Expert
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Your heart is a muscle that requires oxygen and energy to function. This makes it especially sensitive to fluctuations of thyroid hormone, which helps facilitate the delivery of oxygen and energy to cells of the heart.

Thyroid problems are a common cause of heart-related symptoms and conditions that increase your risk of coronary artery disease, heart attack, heart failure, and stroke.

Let’s take a look at the link between your thyroid — the master gland of metabolism — and your heart.


Common heart symptoms in thyroid patients

Several heart-related symptoms and conditions are seen in both hypothyroidism — an underactive thyroid — and hyperthyroidism – an overactive thyroid. They include:

  • Hypertension — chronically elevated blood pressure
  • Mitral valve prolapse — a leaky heart valve that causes palpitations and skipped beats
  • Heart rhythm changes and heart palpitations
  • Heart pain, known as "angina"
  • Pericardial effusion — a collection of excess fluid around the heart


Hypothyroidism and your heart

When your thyroid is underactive, this can affect the heart in a number of ways. Some of the more common heart-related manifestations of an underactive thyroid include:

  • Bradychardia — a slow heart rate
  • Hypotension — chronically low blood pressure
  • Elevated cholesterol — seen in 90 percent of patients with hypothyroidism
  • Elevated triglycerides
  • Mild hypertension — high blood pressure
  • Atherosclerosis — hardening of the arteries
  • Pleural effusion — excess fluid that accumulates in the area around the lungs.


Hypothyroidism and your heart

There are two more severe heart issues related to hypothyroidism.

  • Prolonged QT interval — a heart rhythm condition that can potentially cause fast, chaotic heartbeat, a seizure, and even death.
  • Torsade de pointes — a type of ventricular fibrillation that causes heart irregularities, and can lead to death.


Hypothyroidism and congestive heart failure

One particular complication of hypothyroidism is congestive heart failure. This occurs when your heart muscle isn’t pumping blood as well as it should. This is even more prevalent in thyroid patients who have low levels of triiodothyronine (T3). A number of studies have shown that 30 percent of patients with congestive heart failure have low levels of T3.


Hyperthyroidism and your heart

When your thyroid is overactive, your heart can be affected in a number of ways that over time can lead to blood clots, stroke, heart failure, and heart attacks. Some of the more common heart-related manifestations of an overactive thyroid include:

  • Tachycardia — an elevated heart rate, usually above 100 beats per minute
  • Hypertension — chronically high blood pressure
  • Heart palpitations, skipped beats, flutters
  • Exercise intolerance
  • Shortness of breath on exertion


Atrial fibrillation and hyperthyroidism

Atrial fibrillation is a serious heart condition associated with hyperthyroidism. In atrial fibrillation, instead of pumping, parts of your heart quiver. This can cause rhythm irregularities, rapid heartbeat, and even heart failure. Some studies have shown that patients with hyperthyroidism have a six times higher risk of atrial fibrillation compared to people with normal thyroid function. Atrial fibrillation is seen in up to 8 percent of all hyperthyroid patients, including those with subclinical or borderline hyperthyroidism.


Pulmonary hypertension and hyperthyroidism

Pulmonary hypertension is a serious complication often associated with hyperthyroidism. It refers to high blood pressure in the lungs that can affect your heart’s function and lead to heart failure. In one study of patients with hyperthyroidism caused by Graves’ disease, 65 percent of the patients had pulmonary hypertension.


Treating thyroid-related heart problems

The good news is that most research shows that almost all the cardiovascular changes and increased risks are reversible when your underlying thyroid disorder is recognized and fully treated.

For hypothyroidism that involves the use of a thyroid hormone replacement medication like levothyroxine (Synthroid, Levoxyl, Tirosint), one recent study confirms that restoring TSH levels to normal and treating the hypothyroidism outweighs any risks in terms of benefits for your heart health.


Treating hyperthyroidism-related heart problems

For hyperthyroidism, treatments include antithyroid drugs (like methimazole), radioactive iodine (RAI), or surgery. Typically, use of antithyroid drugs or radioactive iodine treatment can resolve most hyperthyroidism-related heart irregularities within 2 to 3 months.


Other treatments

Some other treatments that may be added to the thyroid treatment include:

  • A beta blocker drug, such as propranolol, to slow your heart rate
  • Digoxin and diuretics to help your heart, and reduce fluid from around the heart and lungs
  • A daily aspirin to prevent blood clots


The heart drug amiodarone

A drug called amiodarone (Cordarone, Pacerone) is an effective medication that restores normal heart rhythms and treats atrial fibrillation and tachycardia. Iodine-rich amiodarone can significantly affect the thyroid. From 5 to 25 percent of patients on amiodarone become hypothyroid, and from 2 to 10 percent become hyperthyroid. Experts recommend that if you are being treated with amiodarone, you should have periodic thyroid testing, whether or not you have a pre-existing thyroid condition.