Men taking Propecia now have more to think about than hair loss-namely, their prostate. A new study has found that the hair-growth product increases the chances for an inaccurate reading on the PSA (prostate-specific antigen) prostate-cancer screening test.

Finasteride, the drug in Propecia, lowers the levels of PSA in the body, so someone with cancer might actually get test results back falsely indicating no need for alarm.

While finasteride lowers the indicator for the test, "it does not raise the risk for cancer," says Leslie D. Michelson, member of the board of directors and former CEO of the Prostate Cancer Foundation. Nor does it make the PSA test itself problematic, he adds.

"There's no need for people to go out and get new tests," Michelson says. "Men just need to tell their doctors that they've been taking Propecia and have their results reinterpreted. This just reinforces the importance of coordinating care among providers and letting all your doctors know exactly what medications you are taking."