According to my informal and very inaccurate measurement, the testicles shrink measurably after 1 to 3 weeks on a pretty low dose of E & Spiro. It has since felt to be even smaller, but not in terms of actual measurement. I think that one's more of a change in feeling in the area after hormones.
Hard erection disappear pretty quickly as well. Can still get an erection with effort and touch down there, but they are relatively soft erection, and one that disappear quickly once stop touching. At 3 months it has gotten to the stage where getting an erection is difficult even with effort.