You will get thousands of replies to this thread. You don't know that there are more PEDS expert in ESB than the entire USADA/WADA organization?
Well why would boxers use hgh or stuff to get more muscles, they would want stuff that improves your stamina or increases your recovery. Things like epo or this other drug I often heard at my gym 7 years ago, susanol or sustanzol something like that. For the use of steroids maybe not the best example but check out how tennis player Nadal used to look several years ago and how he looks now that his former conditioning coach got fired later caught with some peds scandal. He looks much less muscular nowadays but he still plays greatly.