Thyroid Conditions and Heart Disease: What  s the Connection?

Do you have an overactive or underactive thyroid? These conditions increase your risk of cardiovascular (heart and blood vessel) complications that could lead to heart failure. Here’s why it happens, and how it can be treated.

Common Thyroid Conditions

The thyroid gland, located in the front of the neck, produces thyroid hormone. In addition to other tasks, such as controlling energy metabolism, thyroid hormone helps regulate heart function. But thyroid conditions are not uncommon: The American Thyroid Association estimates that about 20 million Americans have a thyroid disease. Most are women, and many are unaware that they have a problem.

Two common thyroid problems are hypo- and hyperthyroid conditions. With an underactive (hypo) thyroid, your thyroid gland does not produce enough thyroid hormone. Symptoms of an underactive thyroid include:

  • fatigue
  • weakness
  • constipation
  • feeling cold
  • weight gain, in spite of a decreased appetite

If you have an overactive (hyper) thyroid condition, you are producing too much thyroid hormone. Symptoms of an overactive thyroid include:

  • weight loss
  • nervousness
  • fatigue
  • rapid heartbeat
  • more frequent bowel movements
  • feeling hot
  • tremors (shakiness)

Heart Symptoms in Thyroid Patients

Both hypo- and hyperthyroid patients may experience cardiovascular (heart and blood vessel) symptoms. In fact, "The most common indication of a misbehaving thyroid is a change in heart rhythm," says New Jersey-based cardiologist William Tansey, MD.

Frequent problems among patients with either underactive or overactive thyroid include atrial fibrillation (an irregular heartbeat that can lead to heart complications), changes in fat metabolism, increased or decreased heart rate, and accelerated atherosclerosis, or hardening of the arteries. These conditions, in turn, can lead to heart failure.

Cardiovascular symptoms in hypothyroid (underactive thyroid) patients may include:

  • High cholesterol
  • Decreased heart rate
  • Reduced blood pressure
  • Impaired blood flow
  • Progression of heart failure

Cardiovascular symptoms in hyperthyroid (overactive thyroid) patients may include:

  • Heart palpitations
  • Atrial fibrillation
  • Angina (chest pain)
  • Increased systolic blood pressure (The “top number,” which measures pressure in the arteries when the heart beats, according to the American Heart Association)
  • Peripheral edema (swelling of the legs, hands, or feet)
  • Congestive heart failure

"Think of the thyroid as the body’s accelerator," Tansey continues. "Too much thyroid hormone and the body speeds up; too little and it slows down." In the case of an overactive gland, Tansey likens the heart’s response to racehorse that is being whipped too hard, or a car engine when you try to go too fast in first gear. There comes a point where the heart simply cannot accelerate any further and the rhythm becomes chaotic, with results like palpitations and atrial fibrillation.

Fortunately, when normal thyroid function is restored in time, cardiovascular abnormalities can be reversed, or at least improved, and the risk of heart failure reduced.

Treating Hyper and Hypothyroid Conditions

In patients with an overactive thyroid gland, treatment may include anti-thyroid medication that blocks thyroid hormone, radioactive iodine treatment to destroy overactive tissue, or surgical removal of the thyroid gland. (When the thyroid gland is removed, thyroid hormone replacement therapy is then necessary to maintain normal hormone levels.)

In those with an underactive thyroid, treatment also includes supplemental thyroid hormone therapy.

Until thyroid function is normalized, cardiovascular symptoms must be treated. For instance, your physician may prescribe cholesterol-lowering medication for high blood levels, and beta-blocker medication can be used to control atrial fibrillation.

William A. Tansey III, MD, reviewed this article. 


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