Levothyroxine is a common medicine used to treat thyroid problems. In fact, it’s one of the most prescribed drugs in the United States.
Many people have a thyroid condition called hypothyroidism, where the thyroid gland does not make enough hormones. Levothyroxine helps by replacing the missing hormone.
But a large study from the University of Michigan has found that if this medicine isn’t carefully managed, it could increase the risk of dying from heart disease.
This is especially important because heart disease is the number one cause of death in the U.S. It affects nearly half of all adults over age 20.
The new study was led by Dr. Maria Papaleontiou and published in JAMA Network Open. Researchers looked at more than 705,000 veterans in the U.S. who were treated with thyroid hormones between 2004 and 2017.
They found that up to half of these patients had hormone levels that were not well controlled. Their thyroid hormone levels were either too high or too low—and both situations can harm the heart.
The study looked at a hormone called TSH, which stands for thyrotropin. TSH helps control how the thyroid gland works. If TSH levels are too low, it means the body has too much thyroid hormone, often because the dose of levothyroxine is too high.
This condition is called exogenous hyperthyroidism. If TSH is too high, it means the body has too little thyroid hormone, which can happen when the dose is too low.
Both high and low TSH levels can hurt the heart. They can cause the heart to beat too fast or too slow, and they can make blood pressure harder to control.
The study showed that people with very low TSH (below 0.1) or very high TSH (above 20) had the greatest risk of dying from heart-related problems. This risk was even higher in older adults, who are more sensitive to changes in thyroid hormone levels.
To make sure the study was accurate, researchers excluded people who already had other conditions that could affect thyroid levels. For example, they left out people with thyroid cancer or those taking drugs like lithium or amiodarone, which are known to change how the thyroid works.
This study shows that treating thyroid problems isn’t just about giving hormone pills. It’s about finding the right dose and keeping the hormone levels in a safe range. If the dose is too strong or too weak, it can cause serious health problems, especially for the heart.
The good news is that this risk can be prevented. Doctors can reduce the danger by regularly checking TSH levels with blood tests and adjusting the medication as needed. Regular check-ups are very important, even if a person feels fine.
This research also shows that thyroid and heart health are closely linked. It supports the idea that thyroid treatment needs to be personalized, especially for older adults. There is no one-size-fits-all approach.
If you or someone you know is taking levothyroxine or any thyroid medication, it’s important to follow up with your doctor. Even if you feel okay, your hormone levels might not be. Keeping your TSH in a healthy range can protect both your thyroid and your heart.
Other research has shown that lifestyle also matters for heart health. For example, some studies suggest that eating eggs may lower heart disease risk. However, some herbal supplements could be harmful to the heart’s rhythm.
Vitamin C might help lower the risk of heart failure, but vitamin E does not have the same effect. Even drinks like espresso may change cholesterol levels.
Overall, this study reminds us that small changes in how we manage medication can have a big effect on health. With regular monitoring and the right dose, people with thyroid problems can live healthier lives and avoid serious heart problems.
If you care about heart disease, please read studies that herbal supplements could harm your heart rhythm, and how eating eggs can help reduce heart disease risk.
For more health information, please see recent studies that apple juice could benefit your heart health, and results showing yogurt may help lower the death risks in heart disease.
