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Metformin monotherapy increased risk for low TSH levels
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Metformin was linked to an increased risk of low thyroid-stimulating hormone levels in patients with hypothyroidism, according to recent study findings published in the Canadian Medical Association Journal.
Laurent Azoulay, PhD, of McGill University in Montreal, and colleagues evaluated 5,689 patients with treated hypothyroidism and 59,937 euthyroid patients to determine the association of low TSH levels with metformin monotherapy compared with sulfonylurea monotherapy.
Among patients with treated hypothyroidism, mean TSH levels at 1 year of follow-up were 2.31 mIU/L (metformin 2.24 mIU/L; sulfonylureas 2.82 mIU/L) compared with 2.03 mIU/L (metformin 2.04 mIU/L; sulfonylureas 2.02 mIU/L) in euthyroid patients.
During follow-up, there were 495 events of low TSH levels among hypothyroidism patients compared with 322 events among euthyroid patients.
Researchers found that metformin was associated with a 55% increased risk of low TSH levels among patients with hypothyroidism vs. treatment with sulfonylurea. No associated risk of low TSH levels was found with metformin treatment among euthyroid patients.
“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, with the highest risk observed in the first 180 days after treatment initiation,” the researchers wrote. “Metformin appeared to have no effect on TSH levels in euthyroid 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.”
Disclosure: The researchers report no relevant financial disclosures.
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