Researchers looked at 31 male participants and found that taking ibuprofen reduced production of testosterone by almost a quarter in the space of around six weeks.
The human brain compensates for testosterone deficiency by producing luteinizing hormone (LH), which sends a signal to the testicles to produce more testosterone.
A study published Monday in Proceedings of the National Academy of Sciences found that regular ibuprofen use may lead to compensated hypogonadism, a condition that can lead to infertility, erectile dysfunction, depression and loss of bone and muscle mass, among other symptoms. To compensate, the pituitary gland stimulates production of more testosterone - but eventually, the mechanism wears out and levels of the hormone drop throughout the body. After 14 days of ibuprofen use, the researchers observed higher blood levels of luteinizing hormone, which regulates the production of testosterone and other hormones.
Although the study continued for six weeks, after just two weeks of taking the doses daily, the group of men taking the ibuprofen developed a hormonal condition which showed a lower testosterone level.
Next, the researchers tested the direct effect of ibuprofen on testicles, using samples that had been taken from organ donors. Men were then divided - 14 in an ibuprofen group, 17 in a placebo group. That number rose to a 23 percent decrease after 44 days.
'Several studies have shown mild analgesics exposure during foetal life is associated with anti-androgenic effects and congenital malformations.
On its own, a study this small would be little more than a call to do more detailed studies. The consistency of the results, however, as well as the earlier epidemiological results, suggest that there might really be an issue here. But researchers are concerned about long-term use among athletes.
The findings are certainly significant, as the 1,200mg of ibuprofen given to the participants each day is far below the suggested daily maximum of 3,200mg per day. The authors speculate that this could have health implications for such men, given the known links between the disruption of such hormones and cardiovascular disease, diabetes and infertility.