1) Wikipedia has some excellent info.. search 'human growth hormone'... they also cite all their sources.. It does help to have specific queries relating... but as an overview that's an excellent place to start.
2) As far as I've read.. No, and also in my personal experience.. No.
'Many scientific studies confirm that GH treatment in adults improves the body composition (increasing the muscle mass and decreasing the fat mass), the bone density, muscle strength, cardiovascular parameters (i.e. decrease of LDL cholesterol), and the quality of life. Using moderate doses there are no side effects.' Studies are cited on wiki
3) If your son is already diagnosed with deficiency, I think it would be a simple matter to express to your doctor you are concerned with a similar deficiency and request the testing.