If you have a headache or muscle pain and you're trying to conceive, you might want to skip the ibuprofen, suggests a new study which found that the painkiller can reduce fertility in men.

Ibuprofen is a popular over-the-counter painkiller (OTC) that belongs to a class of drugs known as NSAIDs (nonsteroidal anti-inflammatory drugs). Ibuprofen relieves pain, lowers fever, and reduces inflammation. Advil and Motrin are two popular brand names.

The new study was an offshoot of research that was originally designed to study the health effects of OTC pain relievers on pregnant women. Those studies found that aspirin, acetaminophen (Tylenol), and ibuprofen all affected the testicles of male children, and increased the risk that they would be born with congenital defects.

For the new study, researchers enrolled male volunteers aged 18 to 35. About half were given a daily dosage of 600 milligrams twice a day — the maximum dosage listed on the label and also the amount commonly taken by professional and amateur athletes. The other volunteers were given a placebo.

Within fourteen days, the luteinizing hormones —  hormones produced in the pituitary gland which stimulate the testicles to produce testosterone — synchronized with the amount of ibuprofen in the blood. Simultaneously, the ratio of testosterone to luteinizing hormones decreased, indicating dysfunction in the testicles.

The ratio decreased by 18 percent after 14 days, but rose to a 23 percent decrease after 44 days.

The hormonal difference created a condition called "compensated hypogonadism," a disorder common in elderly men and associated with reproductive disorders including reduced fertility, as well as depression, and cardiovascular problems, including stroke and heart failure.

Although the researchers believe that the negative effects of ibuprofen can be reversed in those who use it for only a short time, they are unsure if the effects are reversible in long-term users.

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

Several recent studies have linked OTC painkillers, including ibuprofen, with an increased risk of heart attack, and a 2017 study published in the British Medical Journal found it can begin as soon as a week after beginning taking painkillers. The study also found that the higher the dose, the greater the risk.