Taking a common painkiller can disrupt men’s hormones and cause a disorder associated with impaired fertility, CNN reports. A group of 14 young men took the maximum daily dose of the drug ibuprofen for several weeks, and researchers compared their hormone levels with a second group given a placebo. After 14 days, the men on ibuprofen had a reduced ratio of testosterone to luteinizing hormone, which stimulates testosterone production. This imbalance is known as compensated hypogonadism, a condition that normally emerges later in life and is linked to fertility and heart problems. Writing in the Proceedings of the National Academy of Sciences, the authors call for further studies into possible negative effects of hormonal changes caused by ibuprofen.