Metformin is a drug which is prescribed to diabetics and works by lowering glucose production in the liver. However a recent study suggests that it may increase the risk of low levels of thyroid-stimulating hormone (TSH) among patients with an underactive thyroid.
The study was designed to study the effects of metformin on TSH. It involved the study of data compiled on over 74,000 people who took metformin, along with another diabetes drug known as sulfonylurea, over a 25-year period.
Low levels of TSH could lead to an increased risk of heart problems and broken bones. However, a cause-and-effect link was not established in this study.
Among those patients in the study with an underactive thyroid there were 495 incidences of low levels of thyroid-stimulating hormone per year compared with 322 in the normal thyroid group
In Patients treated for an underactive thyroid metformin was linked with a 55 percent higher risk for low TSH levels, compared to those who were taking sulfonylurea for their diabetes.
Dr. Laurent Azoulay, with the department of oncology at McGill University in Montreal, said in a journal news release, “The results of this longitudinal study confirmed that the use of metformin was associated with an increased risk of low TSH levels in patients with treated hypothyroidism. 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.”
However experts argue that the latest findings need further research. Dr. Gerald Bernstein, director of the diabetes management program at the Friedman Diabetes Institute at Mount Sinai Beth Israel, in New York City feels that the study has brought up the question that does the suppressed TSH have clinical significance?
Dr Bernstein further added, “The answer is as follows, millions of people have type 2 diabetes and millions of people have low thyroid and take thyroid pills. And given the multiple millions of people who take both drugs there has been no mass 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.”