A common diabetes pill can radically raise the risk of heart disease, claims a new study.
The study suggested that metformin, which is used to treat Type 2 diabetes, can increase the risk of people with an underactive thyroid suffering from low thyroid-stimulating hormone (TSH) levels.
The researchers surveyed 74,300 patients who received metformin and sulfonylurea, another common diabetes drug, over a 25-year period where 5,689 had treated hypothyroidism, and 59,937 had normal thyroid function.
The study demonstrated that in the group with hypothyroidism, there were 495 incidences of low thyroid-stimulating hormone (119.7 per 1000) per year compared with 322 in the normal group (4.5 per 1000).
Researcher Dr. Laurent Azoulay, from McGill University in Montreal, Canada, said that 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.
Azoulay added that given the relatively high incidence of low TSH levels in patients taking metformin, it was imperative that future studies assessed the clinical consequences of this effect.
The research is published in CMAJ (Canadian Medical Association Journal).