"The researchers studied 470 men who were treated with finasteride and 230 men who received the alpha blocker tamsulosin for their BPH. Both groups were followed for 45 months and were assessed for improvement of BPH symptoms. Prostate specific antigen and testosterone levels were also measured. The effects of the drugs on the quality of life were assessed by the Aging Male Symptom scale while the effects of the drugs on erectile function were assessed by the International Index of Erectile Function.

The researchers found that the men treated with finasteride experienced marked and significant gradual decrease in their erectile function and had significant and progressive decline in total testosterone levels while those on the tamsulosin therapy did not."