I think probably half the league has done them at some time and I think at least half of linemen do them in some form or another.
They do test for them in college just incredibly ineffectively
http://www.forbes.com/sites/daviddi...use-is-rampant-and-little-is-done-to-stop-it/
Again it's numbers, in 1979 the heaviest player drafted weight 272 pounds, in 2013 there wasn't a single offensive lineman drafted who weighed less than 298, that's from Gil Brandt. When he was asked why he responded "PED's". He said diet and nutrition is part of it but a small percentage, the rest is PED's.
I am sure some guys use them to get drafted and then try and stop the problem is most that do that "shrink". Remember Cushing getting caught and the next year his buddy and workout partner showed up to Packers camp 15 pounds lighter and had his worst NFL season? Did anybody really think that was a coincidence?
Last year an unnamed player in the NFL came forward and said HGH is rampant in the NFL he thinks 10-15 guys on every team are using it regularly.
Arian Foster said he saw guys cheat in college and thinks it's common in the NFL. He's a bit of an outlier he says he never used creatine or even protein drinks, he's a Vegan believe it or not.
I think PED's in the NFL are like pot in the NBA or taking cash in NCAA football and basketball, they don't really want to catch everyone that's doing it because if they did, and suspended them, they couldn't play the games.