Men who regularly take the maximum recommended dose of ibuprofen may be at an increased risk of fertility issues.
A total of 31 men between 18-35 took part in the study, published in PNAS. Men who took 1,200 milligrams of ibuprofen daily - the maximum recommended amount, showed disruption in their testosterone production within 10 days. Men who took half the maximum dose saw their testosterone levels fall within two weeks.
In this time, the men developed a disorder known as compensated hypogonadism. This condition occurs when the body is forced to increase its levels of testosterone because normal production in the testes has decreased. Testosterone is a hormone which is important for roles including making sperm.
The study found that luteinising hormone, which stimulates the production of testosterone, increased as the men ingested ibuprofen, while overall levels of testosterone dropped. Luteinising hormone can act as a temporary testosterone replacement. However, over long periods of time, decreased levels of testosterone can lead to adverse effects on the body and possibly infertility in men.
Researchers who led the study stated that the compensated hypogonadism in participants was mild and temporary. However, they are concerned that the condition may become permanent in men who are long-term ibuprofen users.
'Our immediate concern is for the fertility of men who use these drugs for a long time,' said study author Dr David Møbjerg Kristensen, an environmental health scientist at the University of Copenhagen in Denmark.
Further studies will need to be conducted to clarify the effect of ibuprofen on men's fertility, said Professor Bill Colledge, a reproductive physiologist at the University of Cambridge, UK, who was not involved in the study. A precautionary approach should be taken with respect to men taking ibuprofen, he said.
'Based on these data, I personally would be very reluctant to take ibuprofen for longer than the 10 days normally indicated on the packet.'