A study from the University of Michigan has found that the intensity of thyroid hormone treatment may be linked to an increased risk of death from heart-related causes.
Published in JAMA Network Open and led by Maria Papaleontiou, the research highlights the importance of carefully managing thyroid hormone therapy, especially in vulnerable populations.
Thyroid hormone therapy, particularly the synthetic hormone levothyroxine, is one of the most commonly prescribed treatments in the United States. Levothyroxine is used to treat thyroid disorders such as hypothyroidism, where the thyroid gland doesn't produce enough hormones.
While this therapy is essential for many, its potential risks, particularly for heart health, are not well understood.
Heart disease continues to be the leading cause of death in the U.S., affecting nearly half of adults over 20 years old. This study aimed to explore whether the intensity of thyroid hormone therapy could contribute to heart disease-related deaths.
The researchers analyzed data from over 705,000 U.S. veterans who received thyroid hormone therapy between 2004 and 2017.
They observed that nearly half of these patients had thyrotropin levels -- an indicator of thyroid function -- that were outside the normal range. These abnormal levels often indicate over-treatment (low thyrotropin levels) or under-treatment (high thyrotropin levels).
The findings revealed that patients with thyrotropin levels below 0.1 mIU/L or above 20 mIU/L had a significantly increased risk of dying from heart-related causes compared to those with normal thyroid function.
Older patients were particularly vulnerable to these adverse effects, underscoring the need for careful treatment in aging populations.
To ensure accurate results, the study excluded patients with thyroid cancer, as their treatment often involves targeting lower thyrotropin levels to prevent cancer recurrence.
Patients taking medications like lithium or amiodarone, which can interfere with thyroid function, were also excluded.
The study's results emphasize the importance of maintaining euthyroidism -- normal thyroid function -- in patients undergoing thyroid hormone therapy. Over- or under-treatment can have serious consequences for heart health, making it crucial to monitor and adjust treatment as needed.
These findings suggest that the intensity of thyroid hormone therapy is a modifiable risk factor for heart disease. By carefully managing thyrotropin levels, particularly in older patients, healthcare providers can help reduce the risk of heart-related deaths.
This research highlights the need for personalized approaches to thyroid hormone therapy to ensure both effectiveness and safety.
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