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Too much or too little: thyroid problems and the heart
03/29/2006
Too much or too little: thyroid problems and the heart

The thyroid, a butterfly-shaped gland at the base of your neck, is part of the endocrine system, which is comprised of various glands that produce hormones. The thyroid releases thyroid stimulating hormone (TSH) into the bloodstream which carries it to every cell and organ in the body. The thyroid also helps regulate your metabolism, the rate at which your body works.

What does the thyroid have to do with the heart?

The heart is very sensitive to abnormal levels of thyroid hormone, whether too high or too low. This can have a direct effect on heart muscle.

“If you have thyroid disease, the risk for heart disease is increased not only by the thyroid disease, but also by the presence of other risk factors, such as weight gain and lipid abnormalities that result from thyroid disease,” says Palmetto Health Heart Hospital cardiologist Dr. Donald Alexander. “It is best to seek treatment for the thyroid problem and to reduce any cardiac risk factors.”

Hyperthyroidism
If your thyroid releases too much hormone, your metabolic rate increases, resulting in hyperthyroidism, also known as an overactive thyroid. Increased levels of the thyroid hormone stimulate the heart to beat harder and more rapidly. Other symptoms may include weight loss, nervousness, anxiety and hand tremors.

The palpitations are perhaps the most common symptom of an overactive thyroid gland. Prolonged stimulation of the heart with thyroid hormone may cause incoordination within the heart, which can lead to atrial fibrillation. Atrial fibrillation occurs when the heart’s two small upper chambers (the atria) quiver instead of beating effectively. Blood is not pumped completely out, so it may pool and clot, which may lead to a stroke.

“If untreated, this prolonged stimulation of the heart rate and contraction can increase blood pressure and cause angina and heart failure,” says Dr. Alexander. Angina is a condition in which the heart muscle does not get enough oxygen and the patient may feel a discomfort in the chest, throat, neck, jaw or arms. Left untreated, the condition can lead to heart attack.

Hypothyroidism
If your thyroid releases too little hormone, your metabolism slows down, causing hypothyroidism. Slow heart rate and low blood pressure are typical symptoms, yet are not usually noticeable unless detected by your physician.

Prolonged hypothyroidism can cause metabolic changes and may elevate cholesterol. The condition also may cause the heart muscle to weaken, possibly resulting in heart failure.

“The link between thyroid problems and heart disease is well known. Heart function and rhythm can be affected by thyroid problems, and underlying problems of the heart can be unmasked,” says Dr. Alexander.