Did Bio during my school days. 23 is more likely the age when a guys stops growing height wise.... Being 19, I think it's better to be natural... Read more of the training section of this forum...
If your worried about your growth then you might want to just relax on that issue. When you come into the game you come in with everything or nothing...or at least that is the way I like to think of it . If your going for vascular read up on EQ, you might want to check that out.
regardless of your location, I think 19 is too young to start using (IOP) it's your body bro, knock yourself out. I would however ask that you really research this area. 19 YO man you should have a naturally high test level.