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