Maybe youre right. I saw a dose response curve published by Eli Lilly that showed 18iu subq can vary from 40.0 serum level to 70 serum level. I think it also showed that 10iu is like 70% the serum level of 20iu. If there is more substrate for an enzyme, the enzyme will work more effectively. The higher your testosterone level, the more conversion you have to estrogen. The more growth there is the faster it will be deactivated.
I can't find it right now, and either way I think another blood test would be very useful if he is using GH straight from the pharmacy. But yea you might be right, I am not 100% sure.