By Pat Anson, Editor

If you’re a man who uses ibuprofen regularly for muscle pain or  headache, you could be compromising your ability to have children, according to a small new study.

French and Danish researchers enrolled 31 young male volunteers between the ages of 18 and 35 in the study, and gave about half of them 600 milligrams of ibuprofen twice a day -- the highest recommended dose. The other participants were given a placebo.

After just 14 days, the researchers noted signs of hormonal dysfunction in the men who took ibuprofen, who had high levels of luteinizing hormone, which the pituitary gland produces to stimulate testosterone production in the testicles. 

That condition -- known as hypogonadism -- is usually seen in older men who have low testosterone levels. Hypogonadism is associated with reduced fertility, lower sex drive, depression, fatigue and an increased risk of cardiovascular problems.

“We normally see this condition in elderly men, so it raises an alarm,” study co-author Bernard Jégou, PhD, of the French National Institute of Health and Medical Research, told The Guardian. “We are concerned about it, particularly for healthy people who don’t need to take these drugs. The risk is greater than the benefit.” 

Researchers say the disorder was mild in the ibuprofen group and went away when the men stopped taking ibuprofen. But they worry what would happen to men who take the pain reliever for longer periods. Many professional athletes regularly take high doses of ibuprofen.

“Our immediate concern is for the fertility of men who use these drugs for a long time,” said co-author David Møbjerg Kristensen, PhD, a professor of biology at the University of Copenhagen. “These compounds are good painkillers, but a certain amount of people in society use them without thinking of them as proper medicines.”

The study was published online in the Proceedings of the National Academy of Sciences .

“Ibuprofen appears to be the preferred pharmaceutical analgesic for long-term chronic pain and arthritis. Therefore it is also of concern that men with compensated hypogonadism may eventually progress to overt primary hypogonadism, which is characterized by low circulating testosterone and prevalent symptoms including reduced libido, reduced muscle mass and strength, and depressed mood and fatigue,“ the researchers warned.

The same team of researchers reported in earlier studies that aspirin, acetaminophen and ibuprofen affected the testicles of male babies born to mothers who took the drugs during pregnancy.

Ibuprofen is a widely used over-the-counter pain reliever found in brand name products such as Motrin and Advil.