A new study suggests that metformin, a widely used diabetes drug, could be dangerous for men to use if they're planning to have children. The research found a higher risk of genital birth defects in boys whose fathers had likely been taking metformin in the three months prior to conception. More data will be needed to understand whether this link represents a true cause-and-effect relationship and if it should change how the drug is prescribed.
Metformin is a generic drug that's proven to be an invaluable treatment for many people with type 2 diabetes. In combination with diet and exercise, metformin helps keep blood sugar levels in check. It's also often used off-label as a modest weight loss aid and to manage symptoms of polycystic ovary syndrome, a hormonal condition that can raise the risk of insulin resistance and type 2 diabetes. Some data has even suggested that it may help slow down cognitive decline in older patients.
As important as metformin is, no drug is without side effects. And some studies, largely in animals or in the lab, have suggested that the drug could negatively affect the male reproductive system. This new research, published Monday in Annals of Internal Medicine, seems to be the first large study of its kind to look for this potential impact in men.
The study authors analyzed population data from Denmark on over a million births recorded from 1997 to 2016. This data included information on prescribed medications filled by the parents of these children. And when they looked at the outcomes of children born to fathers who had filled a prescription for metformin during the preconception period, they found an overall higher rate of birth defects: about 5.4% for these children, compared to 3.3% of other children.
Maarten J. Wensink , Ying Lu , Lu Tian , et al. Preconception Antidiabetic Drugs in Men and Birth Defects in Offspring, Annals of Internal Medicine (DOI: 10.7326/M21-4389)