I would ditto most of the comments that you received from the other posters.
In my humble opinion HGH is to avoided at all costs.
Getting proper rest, eating mostly FRESH local organic foods, lots of exercise and avoiding the usual "nons" (drugs, alcohol etc.) would help him more than anything.
Most teens don't need multi vitamins if they are getting them from their nutritious diet.
Finally, if you are really concerned, consult your son's health care provider for additional recommendations.