Metformin is a commonly used drug to treat and manage diabetes symptoms. A recent study has found that the drug may raise the risk of low levels of thyroid-stimulating hormone (TSH) among patients with an underactive thyroid.
According to the researchers, low TSH levels may be associated with heart problems and broken bones. Still, the study was not able to establish a cause-and-effect link.
The researchers discovered that among participants with an underactive thyroid, or hypothyroidism, there were 495 incidences of low levels of thyroid-stimulating hormone per year, compared with 322 participants with normal thyroid condition.
The study also unveiled that between patients who received metformin and those who took sulfonylurea for the treatment of an underactive thyroid, metformin was linked with a 55 percent higher risk for low TSH levels.
Dr. Laurent Azoulay of the department of oncology at McGill University in Montreal said that the findings of this longitudinal study has confirmed that using metformin is associated with an increased risk of low TSH levels in hypothyroidism patients. "Given the relatively high incidence of low TSH levels in patients taking metformin, it is imperative that future studies assess the clinical consequences of this effect," Azoulay said in an official press release.
Meanwhile, two experts note that further research is needed to validate such findings.
According to Dr. Gerald Bernstein, director of the diabetes management program at the Friedman Diabetes Institute at Mount Sinai Beth Israel, New York City, it is important to ask: "does the suppressed TSH have clinical significance?"
The answer, Dr. Bernstein said, is that millions of people have type 2 diabetes, and millions also have low thyroid and take medication. This fact suggests that there is no massive clinical issue.
"This study did not contain any measurements of the two forms of thyroid hormone in the blood. That data might help clarify why the TSH is suppressed," Dr. Bernstein added.
