Levothyroxine is a common medicine that replaces thyroid hormones in the body. It has been one of the top three most prescribed drugs in the United States for more than ten years.
This shows how common thyroid problems are. At the same time, heart disease is still the number one cause of death in the country. Almost half of all adults in the U.S. over the age of 20 have some form of heart disease.
Now, a new study from the University of Michigan has found something important—thyroid treatment could raise the risk of dying from heart problems if not managed carefully.
People with low thyroid hormone levels, a condition called hypothyroidism, are often treated with levothyroxine to bring hormone levels back to normal. But treatment doesn’t always go perfectly. Sometimes the dose is too strong, and sometimes it’s too weak. That can create problems for the heart.
Doctors use a hormone called TSH (thyrotropin) to measure how well the thyroid is working. If the TSH level is too low, it means the body may have too much thyroid hormone, possibly due to too much medication.
This is called overtreatment, and it can strain the heart. On the other hand, if TSH is too high, the body is not getting enough thyroid hormone, which means the treatment is too weak. This can also hurt the heart.
The study, led by Dr. Maria Papaleontiou and published in JAMA Network Open, looked at medical records from more than 705,000 U.S. veterans who took thyroid hormone therapy between 2004 and 2017. The researchers found that up to half of these patients had TSH levels that were too high or too low.
These people had a higher chance of dying from heart problems compared to those whose TSH levels were in the normal range. The risk was greatest when TSH was very low (below 0.1) or very high (above 20). Older adults were especially at risk.
To make sure their results were correct, the scientists left out patients who had thyroid cancer, since they often take higher doses on purpose. They also excluded patients on certain medications that affect thyroid levels, like lithium or amiodarone.
This study is important because it shows that how much thyroid hormone someone takes can affect their heart health. The good news is that this is something doctors can control.
By keeping TSH levels in a healthy range, doctors may be able to lower the risk of heart-related deaths. It’s a reminder that patients should get regular blood tests and have their treatment plans reviewed often, especially as they get older.
This research is part of a bigger effort to understand what keeps the heart healthy. Other studies have found that eating eggs may protect the heart, while some herbal supplements could be harmful. Vitamin C might lower the risk of heart failure, and even drinking espresso coffee may change cholesterol levels.
In the end, the thyroid and the heart are closely connected. Taking care with thyroid treatment—especially making sure TSH levels stay steady—can help prevent serious heart problems.
If you care about heart health, please read studies about how vitamin D influences cholesterol levels, and what we know about egg intake and heart disease.
For more health information, please see recent studies about best supplements for heart disease prevention, and wild blueberries can benefit your heart and brain.
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