I've always been curious of the HGH, as I've been told a doctor can actually prescribe it to you.
Yeah, it is actually used for some medical issues. There are some rare disease where people don't fully develop or are late developing and HGH helps with that.
Like many drugs, they were developed or discovered to cure one thing, then discovered to provide effects for something completely unrelated and end up being used/abused for that.
Viagra was originally being developed for heart issues, hence the increased blood flow, just took effect in the wrong area.