The Reverse Steroid (M seeking F)

So this idea comes from that age old tidbit of knowledge that steroid use causes genital shrinkage in men in exchange for larger muscles/bodies in general. But what if they developed a reverse version? A steroid that caused an adult male to revert in appearance to that an adolescent but caused extreme growth of their genitals? The idea is a college guy has to take these pills for some medical condition, but still has a healthy sex drive despite his youthful appearance. He seeks out female partners, really taking anything he can get from MILFy teachers looking for a cute little play thing, to co-ed's looking to experiment. This is definitely an idea designed to be played up for laughs as well as smut, and I do want to say that all parties would be of legal age regardless of appearances.