weve touched on this before on here, its a big can of worms that has no definate answer....
the main reason that know one knows is most dont get there sperm count tested before they start abusing steroids ( i know i never ), so then you try and get babied up,...then cant and go and get tested then blame the gear, where u could have been sterile or low before u ever started.. you truely never know unless u do all the tests before u ever start..
i'll just like to add, i know many a doorman/competitior/gym rat who have more or less been constantly on, never done a pct, and are still knocking out kids in there 40's.. thats not saying that you or my self will be the same?...