Balding men who use the hair-growth drug finasteride need to mention this to their doctor when having a blood test for prostate cancer: The medication could artificially suppress levels of the protein that signals a possible tumour.
As a result, all finasteride users who have a test for this protein – -- known as prostate-specific antigen (PSA) – need to have the results multiplied by two, says Dr. Claus Roehrborn, chairman of urology at the University of Texas Southwestern Medical Center in Dallas.
Finasteride was originally developed as a treatment for an enlarged prostate. It is marketed under the brand name Proscar for this purpose, and as Propecia for hair loss. Doctors already knew finasteride lowered PSA levels at the higher doses used in prostate treatment, but Roehrborn and his colleagues have found the same effect at the lower doses used for hair loss.
"The impact of finasteride on PSA levels is significant," Roehrborn says. "When doctors ask for their patients' medical history, they need to ask if they have taken any drugs for hair loss."
The researchers studied 355 men who took finasteride or inactive pills for 48 weeks. Men in their 40s had a 40 per cent decrease in PSA levels, while men ages 50 to 60 years had a decrease of 50 per cent.
Roehrborn and his team say more research is needed to assess the effects of low-dose finasteride on PSA levels beyond 48 weeks of treatment.
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