In a new study, researchers found that treatment of heart attack patients for a common condition, an underactive thyroid, with drug levothyroxine does not improve heart muscle function, so is unlikely to be of benefit.
The research was carried out in six UK hospitals and led by experts at Newcastle University.
Mild or subclinical hypothyroidism is a condition in which the body doesn’t produce enough thyroid hormones and is very common affecting approximately 10% of the adult population.
Management of the condition is currently haphazard due to the lack of high-quality evidence either for or against treatment.
Some clinicians may treat whereas others may not—and this is particularly the case in high-risk conditions such as heart attacks.
Previous studies have suggested that patients with cardiac problems, including heart attacks, and subclinical hypothyroidism are at higher risk of death.
And so, current guidelines suggest that these patients should be treated with levothyroxine.
This study demonstrates that treatment with levothyroxine does not improve cardiac function in patients who have had a heart attack and therefore is unlikely to be beneficial.
In the trial, 95 patients were recruited with 46 receiving levothyroxine and 49 a placebo. After 12 months, heart function improved in both groups—but there was no greater improvement in those receiving levothyroxine.
Limitations of the trial include the low dose offered initially which may have reduced the therapeutic effect and there may be a bigger improvement in patients were patients to start treatment sooner (average 17 days after a heart attack).
In addition, 4 in 10 patients with subclinical hypothyroidism on the initial blood test had normalized their levels when rechecked a few days later.
The results demonstrate that there are no significant improvements for patients with heart attacks who are given levothyroxine.
The findings will help doctors reconsider offering treatment with levothyroxine to tens of thousands of patients with subclinical hypothyroidism worldwide.
To any patient who has had a heart attack and has been diagnosed with subclinical hypothyroidism, the researchers advise that they consult their GP on whether levothyroxine is likely to be of benefit.
One author of the study is Dr. Salman Razvi, Senior Lecturer and Consultant Endocrinologist, Newcastle University.
The study is published in JAMA.
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