HGH may not work effectively on certain patients (specifically those who are at or below -2SD of the average height; otherwise, sensible doctors would not be willing to inject HGH into your bodies) because of factors like insusceptibility to HGH, pre-existing normal HGH levels, early fusion of growth plates, and other reasons.
However, if it could have an effect on me, someone who would prefer Schizophrenia over being short, then the potential side effects such as heart disease, Acromegaly, or diabetes would feel like a mere walk in the park for me.