Penis tissue and all tissue of the reproductive tract - prostate, seminal vehicles, testes, etc - are androgen dependent. They need androgens -- of which DHT is the more potent one -- for tissue maintenance, not just in development. Androgen deprivation leads to apoptosis - cell death. This of course is finasteride's original indication - to shrink the prostate through apoptosis. The same effect is observed in penile tissue. There are countless rat studies confirming this effect of finasteride (shrinking the penis) and also on the importance of DHT. The effect is also observed in humans who have undergone androgen deprivation therapy to fight off prostate cancer. When penile tissues undergoes apoptosis the dead cells are replaced by scar tissue. This can be observed as fibrosis and is an objective measure of tissue damage. Note that these effects are the typical mammalian response to finasteride, are likely to be cumulative, and are NOT a feature of PFS per se, although the effect can be even more pronounced in people with PFS, as their 5ar enzyme may be permanently and completely deactivated.
I have tried various supplements but nothing has worked. Tribulus works a little bit but it stops working after a while. Also, transdermal DHT has alleviated my extreme joint pain.