Major Diabetes Drug Taken by Men Linked to Rare Genital Defects

A recent large-scale study suggests that taking a significant diabetes drug, metformin, increases the risk of birth defects before conception.

Metformin is a first-line diabetes drug that has been widely used for decades. According to a recent study, it may boost the risks of birth defects, especially rare genital defects, in offspring of men that took the drug during sperm development.

Metformin Plays a Role in Birth Defects According to Large-Scale Study

According to a recently concluded large-scale Danish study published in the journal Annals of Internal Medicine, titled "Preconception Antidiabetic Drugs in Men and Birth Defects in Offspring," sons born to men who took metformin during sperm development were three times more likely to have genital birth defects compared to unexposed babies.

Hypospadias, a genital defect, occurs when the urethra doesn't exit from the tip of the penis; relatively rare, it occurs in 0.9% of all babies born whose biological fathers took the first-line diabetes drug three months before conception. However, epidemiologists explain that the recent study's findings are vital to tens of millions of people across the globe that take metformin, chiefly for people diagnosed with type-2 diabetes.

Germaine Buck Louis, a reproductive epidemiologist from George Mason University, wrote in the accompanying article that metformin is widely used even by young men due to obesity issues. Hence, the potentially huge source of exposure for the next generation.

However, Louis and other scientists interviewed stressed that the paper's findings are preliminary and observational, needing more work to be corroborated. Adding that factors besides metformin could have played a significant role in the findings. Scientists also cautioned men with diabetes against abruptly stopping their metformin intake before attempting to conceive.

Maarten Wensink, first author and an epidemiologist at the University of Southern Denmark, explains that metformin is a safe drug; it's cheap and does what it needs to do. Adding that abruptly stopping metformin is a complex decision and should be advised by a physician.

Metformin; a Major Diabetes Drug

Metformin, a synthetic compound, lowers blood sugar levels by boosting a person's insulin sensitivity. Its use has skyrocketed parallel to the obesity epidemic and attendant diagnoses of type-2 diabetes. In the US in 2004, 41 million prescriptions for the drug were written; in 2019, it reached 86 million.

Metformin has been used widely since the 1950s; however, this is the first large-scale study to rigorously analyze any paternally mediated impact the drug has on human birth defects. Although the use of metformin skews to older people, the rise in diabetes means that more men have been taking the drug during their reproductive years.

Researchers analyzed records from over 1.1 million babies born in Denmark between 1997 and 2016, using the country's comprehensive medical registries connecting data on births, paternal metformin prescription, and birth defects. The team found that in the 1451 offspring of men that filled metformin prescriptions during the 90 days before the offspring's conception, when the sperm are being made, 5.2% rate of birth defects compared to the 3.3% of unexposed babies.

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