Chance of higher risk for Propecia side effects?

Decrease in penis and/or testicle size is not a reported side effect of Propecia.The major side effect is decrease in sex drive and/or erectile dysfunction.The reported incidence is 1-2%.

No I dont think so that men with small penis and small testicles have a higher chance of receiving side effects from Propecia...But you may have Post-finasteride syndrome, occurs in men who’ve taken finasteride to treat hair loss by a chance of %4-5. That may causes some symptoms include: loss of libido, erectile dysfunction, depression, suicidal ideation, anxiety, panic attacks, Peyronie’s disease, penile shrinkage, gynecomastia, muscle atrophy, cognitive impairment, insomnia, severely dry skin and tinnitus. The condition often has a life-altering impact on victims and their families, such as job loss and the breakup of marriages and romantic relationships..

Propecia inhibits the transformation of testosterone into DHT, resulting in more testosterone circulating and less DHT. Decrease in penis size and/or testicle size is not a listed side effect of propecia. I would not expect this side effect to occur. This has never occurred in my practice.  

No I don't believe that shrinking the penis is real, at least I have not heard that from my patients who have been using this drug for years.