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Published on May 07, 2018

Thyroid hormone implicated in hardening of arteries

A new Dutch study published recently in the American Heart Association’s journal Circulation identified the hormone, free thyroxine (FT4), as a possible culprit in the development of atherosclerosis, or hardening of the arteries.

This is the first study to make that association.

Researchers have known for years that risk factors for coronary artery disease include high cholesterol, high blood pressure, diabetes and smoking. While certain thyroid hormones like TSH (thyroid stimulating hormone) have previously been associated with heartbeat irregularities and heart disease, the role of other thyroid hormones has been less clear.

The Rotterdam Study research followed more than 9,420 participants for an average of nine years, looking for evidence of heart disease, stroke and arterial disease. They were interested in the role of TSH and FT4 in the development of atherosclerosis, particularly as it occurred over time.

During the study, 612 patients died of heart disease and another 934 suffered a heart attack or stroke.

Researchers found that those with normal to high circulating levels of FT4 were twice as likely to develop atherosclerosis. High FT4 was also linked to an 87 percent increased risk of having a heart attack or stroke, and doubled the risk of dying from one. The findings were independent of any cardiovascular risk factors and were consistent even when there was otherwise normal thyroid function.

The findings were not surprising to Hyannis cardiologist Peter Chiotellis, MD.

“The thyroid is the driving force of your entire body, producing hormones that affect your metabolism, heart rate and energy level,” he said “We know that an overactive or under-active thyroid can affect your whole body. So, it’s not surprising that we see it affect the heart.”

How The Thyroid Functions

According to the American Heart Association, atherosclerosis is the most common type of coronary heart disease, responsible for the deaths of more than 370,000 Americans annually. It is a slow, progressive disease that may begin in childhood.

So, how is this finding useful in understanding the thyroid-heart health link? To answer this, it is important to know a little bit about how the thyroid functions. The thyroid is a butterfly-shaped gland located on your neck just under your Adam’s apple. Despite it’s small size, it plays a big role in your health.

TSH is the most common measurement of thyroid function. Too much TSH present in the bloodstream indicates an underactive thyroid, or hypothyroidism.

“Patients with hypothyroidism often attribute their symptoms to something else. They are usually tired and dragging, which can happen in many other conditions,” said Dr. Chiotellis.

“We know that low thyroid function has already been linked to unfavorable levels of cholesterol and poor body mass index (BMI),” he added. “The slowing of your metabolism may impact your ability to process cholesterol, increasing your risk for heart disease.”

Conversely, too little TSH in the bloodstream indicates an overactive thyroid, or hyperthyroidism. There are many symptoms, but a rapid and irregular heartbeat is one of the more worrisome ones.

Whenever a patient is diagnosed with a type of irregular heartbeat called atrial fibrillation (AFib), the first thing Dr. Chiotellis does is order a thyroid test.

Treatment usually involves caring for both the underlying thyroid disease and the rapid heartbeat at the same time. This can be done with certain medications, but may also require cardioversion – a procedure that uses electric shock to restore normal heart rhythm.

May Lead To Heart Failure

In extreme cases, untreated hypothyroidism can lead to heart failure.

“People with mild hypothyroidism aren’t necessarily going to develop heart failure. The risk happens when you have heart disease and develop hypothyroidism together,” said Dr. Chiotellis. “These patients usually have a TSH of 10 or more.”

When measured in a blood test, normal values for TSH range from 0.4 to 4.0 milli-international units per liter (mIU/L), according to the National Institutes for Health (NIH).

While the findings of the Rotterdam Study suggest that regular screening of FT4 could be a way to identify people at increased risk for atherosclerosis, it is premature to say so. This study consisted only of a white, Dutch population, making it generalizable only to that population.

In the meantime, self-care and advocacy are the best things any of us can do to maintain both thyroid and heart health.

“The people with the biggest risk for development of cardiac issues are those who do not follow-up regularly with their primary care doctors. They miss regular screening opportunities, which can catch these things early at a time where they can easily be treated,” said Dr. Chiotellis.

He advises people to talk with your primary care doctor and find out if thyroid screening makes sense for you.

“Keeping your thyroid healthy is not something you can control, but making sure it is followed up on and treated is the best way to prevent heart issues,” he said.