Study raises metformin concern

Researchers have added evidence to a suspected link between metformin and an increased risk of low thyroid-stimulating hormone (TSH) levels in patients with hypothyroidism.

Their study in the CMAJ (Canadian Medical Association Journal) shows that in patients with treated hypothyroidism, metformin monotherapy is associated with a 55% increased risk of low TSH levels compared with treatment with sulfonylurea.

Metformin therapy did not appear to affect people with normal thyroid function.

They base the finding on data on 74,300 patients