Definitely T causes prostate changes (enlargement), and I've seen it in myself. I keep up on the PSA and the other unpleasant but necessary checkup, and it's so far, just normal prostate enlarging that happens after your 30s & into 40s. If you get an infection of prostatitis, (not related to AAS or meds that I know of), the symptoms would be pain and really sudden change with difficulty in getting pee started, or sometimes being totally plugged off and needing a catheter. Also it can cause semen to be bloody or smelly. That's an infection that needs antibiotics, and sometimes an injection of antibiotics into the prostate itself. Regular enlargement is just part of life for most all men, and we learn to cope with it. As far as sexual function, the reduced semen is also an effect of AAS, but that's another issue. Just an off-topic mention: Prozac is a classic cause of reduced semen and VERY long-time to ejaculate; often too long. But if you're 18 and tend to blow your load as soon as your GF grabs your belt buckle, a low dose of Prozac sometimes gives you more time...
Charles