Effects of Oral Finasteride On Erectile           
Function In a Rat Model

Here is another important, interesting and innovative research
project.  Once again, conducted in a country other than the
United States. I have seen this study quoted in a number of
websites usually with the sensational sounding headline
something along the lines, "Baldness Drug Causes Penis to
Shrink."  This type of reporting simply confirms why it is critical
to go beyond the headline or abstract and carefully read the
entire report which appeared in the Journal of Sexual Medicine
2012.  The research was performed in China .  

In reading the following, please remember that my primary
interest in writing this website is Peyronies Disease.

Many clinical studies of human males have reported finasteride
usage is related erectile dysfunction, but there have been
few animal studies that have taken this approach.  Rats can be
sacrificed and the tissue examined. Obviously, this can not be
done with humans.  With the cautionary note that rats are not
men and may have different reactions to finasteride, we will
examine the results of this study. Secondly, this was a short
term study as the rats were only given finasteride for 4 weeks.     

  • One hundred (100) adult male rats were divided in 4 equal size groups. 1)
    control  2) castration  3) castration with testosterone replacement and 4)

  • In this model the finasteride group was given the drug for 4 weeks and then
    sacrificed.  To better test the potential of finasteride on erectile function of
    normal men this study simulated the intake pattern and dose of finasteride
    used in humans.

  • For simplicity sake I am going to emphasis outcomes between groups #1
    the control, and group #4 rats given finasteride  

  • There was no significant difference in testosterone levels between Group 1
    and Group 4. But, there was a significant difference in DHT levels between
    these groups.  This is the first study to measure the DHT levels in laboratory
    rats who have ingested finasteride    

  • There were no significant changes in the smooth muscles and connective
    tissue in the finasteride treated rats

  • Finasteride intake did not appear to affect erectile response to electrical
    stimulation of the cavernous nerve

  • Intake of finasteride did shrink the prostate. Well I should hope so because
    it is given to men to shrink their prostate so they can have any easier time
    peeing (Proscar)

  • As the Corpus Cavernosum is part of penis somewhat affected by Peyronies
    Disease this chart represents one of the more important findings in the
    study as it relates to our disease.  The Tunica Albuginea is of primary
    concern, but not mentioned in the study.   
As usual when sexual dysfunction and penile abnormalities are  
investigated the topic of Peyronies Disease is ignored.  This study is
no exception. The study was concerned with penile smooth muscle
and connective tissue in the Corpus Cavernosum and did have small
pictures of the Tunica Albuginea.  Not as an indicator of Peyronies,
but as a view of another penile tissue. This study did not contain
any discussion of changes to the Tunica Albuginea. However, since
the Tunica is the area most affected by our disease, I did arrange to
have these 2 photos enlarged.

Picture 1 is of the control group Tunica Albuginea rat tissue and
Picture 2 is of Tunica Albuginea rat tissue where finasteride was

Picture 1

Picture 2