According to the results of a study published in the journal Lancet Oncology, Propecia® (finasteride 1 mg/day) appears to reduce serum levels of prostate-specific antigen (PSA) to a similar extent as Proscar® (finasteride 5 mg/day). 

Men 50 years or older in the U.S. are often offered prostate-specific antigen (PSA) testing for the early detection of prostate cancer. The PSA test measures proteins that are produced and shed by the prostate. PSA levels tend to be elevated when prostate cancer is present, but levels can also be elevated in benign (non-cancerous) conditions affecting the prostate.

Propecia and Proscar contain different doses of the drug finasteride. Propecia, which comes in 1 mg tablets, is used to treat male-pattern hair loss. Proscar, which comes in 5 mg tablets, is used to treat benign prostatic hyperplasia.

Use of Proscar is known to reduce serum PSA levels. This effect on PSA needs to be taken into account when interpreting the results of PSA tests, and researchers have proposed ways to adjust PSA results in men taking Proscar.

The effects of Propecia on PSA levels are less well understood. To evaluate the effects of Propecia on serum PSA level, researchers conducted a clinical trial among 355 men between the ages of 40 and 60. All study participants had male-pattern hair loss. Two hundred eighty-five of the men were assigned to take Propecia for 48 weeks, and 70 were assigned to take a placebo (sugar pill).

• Among men taking Propecia, PSA levels declined by 40% among 40–49 year olds and by 50% among 50–60 year olds.
• Among men taking placebo, PSA levels remained stable in 40–49 year olds and increased by 13% in 50–60 year olds.

The researchers conclude “In men aged 40–60 years, 1 mg/day finasteride [Propecia] for 48 weeks lowers serum PSA concentration.” The effect of Propecia on PSA level will need to be taken into account when interpreting PSA test results. Men who undergo PSA testing should tell their doctor if they are taking Propecia or Proscar.

The researchers recommend additional research to determine how Propecia affects PSA beyond 48 weeks of treatment.

Reference: D’Amico AV, Roehrborn C. Effect of 1 mg/day Finasteride on Concentration of Serum Prostate-specific Antigen in Men with Androgenic Alopecia: A Randomised Controlled Trial. Lancet Oncology [early online publication]. December 5, 2006.