Looking at the three links offered by Snerg, the report National Library of medicine
seems to say a man with low testosterone will fare better during treatment. However, this is a study of 137 men with aggressive stage 4 prostate cancer (Gleason 10 (5+5) so it is unclear whether they mean the low testosterone is keeping the cancer in check or something else.
Review of health risks of low testosterone and testosterone administration
Testosterone and prostate cancer: an evidence-based review of pathogenesis and oncologic risk
say that TRT does not encourage creation of prostate cancer. The last link says that on an experimental and consensual basis TRT might be tried for select prostate cancer patients.
From the real world with a few million patients, we find that prostate cancer thrives where there is testosterone and "hibernates" when the testosterone is removed. The most common means of slowing prostate cancer growth is either chemical or surgical castration. Chemical castration (hormone treatment, ADT) is pretty much reversible.
I was diagnosed with stage 2b, Gleason (3+4) 7 in October 2019. I have no references on my testosterone level as my PCP has his head where the sun doesn't shine. The cancer was in a location that made me uncomfortable so I went on hormone treatment to pause growth until I could finish radiation treatment. My testosterone was too low to measure for 6 months.
Men with advanced cancer may go on hormone treatment for the remainder of their lives to keep the cancer at bay.
Low testosterone leads to all the symptoms other posters have listed and is a normal thing for older men as their testosterone level goes down. With no testosterone, for the short term we experience:
Total lack of sexual interest
Fat to the belly and possibly the breasts
Big time fatigue
Possible muscle and bone loss
Possible brain fog
Sound familiar? MENOPAUSE
We normally ease into this anyway with age, but with hormone treatment it comes crashing in all at once. Long term lack of testosterone is similar to being post menopausal.
We really don't need testosterone for sex, but without testosterone we forget about sex. No interest. The upside is that when we are castrate we need more frequent sex, or at least erections, to maintain ability to have erections. I went on a regime of at least one good erection a day which kept me and my wife busy for six months.
So now I have been off treatment for 19 months, have T of 300-400 and am fully functional, though I think my libido is a bit low. I'm not sure because I learned to do it without libido when I was castrate. It's nice to be back to morning erections,though.