Levothyroxine is a man-made version of a thyroid hormone. It’s one of the most prescribed medicines in the United States and has been in the top three for the past ten years. This shows how common thyroid problems are.
At the same time, heart disease is the number one cause of death in the U.S. It affects nearly half of all adults over the age of 20. A new study from the University of Michigan has found a worrying link between thyroid hormone treatment and a higher risk of dying from heart problems.
Doctors often give thyroid hormone therapy to people with hypothyroidism—a condition where the thyroid gland doesn’t make enough hormones. But sometimes, this treatment causes the body’s TSH (thyrotropin) levels to go too high or too low. TSH is a hormone that helps control how the thyroid works.
When TSH levels are too low, it can lead to a condition called exogenous hyperthyroidism. When they are too high, it means the hypothyroidism isn’t well controlled. Both situations can put extra stress on the heart.
The study was led by Dr. Maria Papaleontiou and published in JAMA Network Open. It looked at data from more than 705,000 U.S. veterans who received thyroid hormone treatment between 2004 and 2017.
The researchers found that up to half of these patients had abnormal TSH levels—either too high or too low. These patients had a greater chance of dying from heart-related issues compared to those whose TSH levels were in the normal range.
The risk was especially high for people with TSH levels below 0.1 or above 20. Older adults were even more at risk, which shows how important it is to manage thyroid hormone treatment carefully in this group.
To make sure their results were accurate, the scientists left out certain people. They didn’t include patients with thyroid cancer because low TSH levels are sometimes used on purpose to prevent the cancer from coming back. They also left out people who were taking medicines like lithium or amiodarone, which can affect the thyroid.
This research shows that how strong the thyroid treatment is can be a risk factor for heart problems. The good news is that this risk can be controlled. By watching and keeping TSH levels in the normal range, doctors might help lower the chance of heart-related deaths in people using thyroid hormone therapy.
It’s important for doctors and patients—especially older adults—to work together on a personalized treatment plan. Regular checkups and blood tests can help make sure thyroid levels stay stable.
This study is a reminder that the thyroid and heart are closely connected. If thyroid hormone treatment is too strong or too weak, it can hurt the heart. Getting the balance right is key.
Other studies have looked at ways to support heart health. For example, eating eggs might lower heart disease risk, and Vitamin C (but not Vitamin E) may reduce heart failure risk. Some herbal supplements, however, might be harmful to heart rhythm.
This new research helps doctors better understand how to protect the heart while treating thyroid problems. With careful monitoring and smart treatment choices, patients can avoid serious heart issues.
If you care about health, please read studies about the benefits of low-dose lithium supplements, and what we know about egg intake and heart disease.
For more health information, please see recent studies about potatoes and high blood pressure, and results showing 6 best breads for people with heart disease.
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