While your primary concern should by on the long term health of your son (because, at 20, most kids think that they are bulletproof and know everything), there are secondary concerns that you should have. Once he gets on the juice, he's going to be susceptible to testing positive on random drug test (and yes, they do not test enough and most guys get around them by cheating anyway), which would/could remove any scholarship from him, banned from the team, kicked off of campus. As well, if he gets caught in possession of the drugs, they are considered a controlled substance and he will be facing some expensive and serious legal/criminal consequences. All it takes is getting into an argument with someone who knows you are doing drugs and a vindictive/retaliatory call to the authorities and you are basically screwed.
http://en.wikipedia.org/wiki/Anabolic_steroid