Levothyroxine is a man-made thyroid hormone that helps people whose bodies do not make enough of this hormone naturally. It is one of the most commonly prescribed medicines in the United States, showing just how widespread thyroid problems are.
At the same time, heart disease is the leading cause of death in the country. It affects nearly half of adults aged 20 and older. A new study from the University of Michigan has found a worrying link between how much thyroid medicine people take and their risk of dying from heart-related problems.
Thyroid hormone therapy, like taking levothyroxine, is often used to treat hypothyroidism, a condition where the thyroid gland does not produce enough hormones. To manage this, doctors look at levels of a hormone called TSH (thyrotropin), which helps control the thyroid. If the treatment pushes TSH levels too low or too high, it can harm the heart.
Low TSH levels can lead to a condition called exogenous hyperthyroidism, which means the body has too much thyroid hormone due to medication. High TSH levels mean there is not enough hormone in the body, causing continued hypothyroidism. Both extremes can strain the heart and increase health risks.
In the study, researchers looked at data from over 705,000 veterans in the U.S. who were on thyroid hormone treatment between 2004 and 2017. They found that about half of these patients had TSH levels that were not in the normal range. These people had a higher risk of dying from heart-related causes than those with normal levels.
Patients with very low TSH levels (below 0.1 mIU/L) or very high levels (above 20 mIU/L) had the highest risk. Older adults were especially at risk, which shows why it’s so important to carefully manage thyroid treatment in older patients.
To make sure the study results were accurate, the researchers left out certain groups of people.
For example, they did not include people with thyroid cancer, because these patients are often kept at low TSH levels on purpose to prevent the cancer from returning. They also excluded people taking medications like lithium or amiodarone, which can affect thyroid function.
The big message from this study is that how much thyroid medicine someone takes can be adjusted—and that getting it right could help lower the risk of heart disease. This means doctors and patients should work closely together to keep TSH levels in the normal range.
This research shows that thyroid health and heart health are connected. Too much or too little thyroid hormone can be dangerous. That’s why it’s important to have regular blood tests and follow-up visits with your doctor, especially if you’re older.
Other studies have looked at ways to protect the heart too. Some found that eating eggs might lower the risk of heart disease, while some herbal supplements can harm heart rhythm. One study showed that vitamin C may help prevent heart failure, and another found that espresso coffee could affect cholesterol.
All these studies help us understand how to stay healthy. For people taking thyroid medicine, this new research is a strong reminder that keeping your hormone levels stable is key to protecting your heart.
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.
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