If your genitals are still "growing" then you are much too young to be taking steroids.
That being said, testosterone administered to the body will eventually cause a shutdown of your HPTA, in turn shutting down your natural testosterone production. This is temporary. In order to avoid the "shrink", steroid users inject HCG, which stimulates the Leydig cells and in turn stimulates your nuts to create goodies (and thus plump back up and drop lower).
Real, authentic HCG is the direct connection to stimulating your LH and getting those nuts plump and low.