If you take HgH when you're younger, you're just retarding your own GH production. If you take it in quantites above "youthful levels" youre going to suffer from acromegaly, or if you take it when youre really young, giantism, with acromegaly. So its pretty pointless (or dangerous) to take when you have naturally "youthful" levels.
Basically kids make tons of this stuff, and they dont need more, but in an adult you only make it in small quantities. Now starvation, inversion therapy, ah..eating very little 6 six times a day, getting 12 hours or more sleep per day, those can raise GH levels in adults, but not to the point of say when you were 18. I use ~18 because generally most (but not all) distal bone growth in women has stopped by then. GH has dropped off, but not significantly to where your skin is starting to loosen, your hair grows slower, you're losing more muscle than you're building, ect ect.
You wouldnt want to take say, a 16 or 12 year old's levels because you dont need to mature bones and organs beyond their adult levels, thats what causes acromegaly, which contrary to wanting bigger hands and feet, you dont want. Granted you do want a certain "organ" to mature to an adult level, but you dont need the systemic levels to do that. The only reason you would need it at all, is it seems to help fool your body into thinking its a boy rather than an adult woman, with the testosterone. If youre still a girl, its not such a big leap to switch to boy. Basically GH only effects your age, not your genetics -unfortunately. Or, as I have already eaten crow once, for not keeping up on things, thats what we thought in the 90s. Does anybody have links to more modern studies that might refute this?