Hi John,

Dosage is dependent on Body Surface Area (BSA).  That is why his dosage will increase as he gets bigger.  If his labs show that he is oversuppressed, you'll take his dosage down a bit.  CAH won't make him any more succeptable to infection unless he is chronically very oversuppressed, which can suppress the immune system.  If you are keeping tabs on his blood levels, this won't happen.

My husband has always believed that vigorous exercise is good for whatever ails you.  I have become a believer myself as I've seen how regular aerobic exercise has benefitted my children.  Many CAH children have trouble with a little extra weight, which can be a side effect of imperfect maintanence.  Regular exercise can help prevent that problem.  Being physically strong can also help with the belief that their bodies are powerful and wonderful instead of just flawed by the CAH.  We hope we're starting them on a healthy lifestyle that will stay with them into adulthood. 

As far as exercise affecting your son's need for meds, we've found that our girls' dosages have gone down as their physical fitness has improved.  We are fanatical about hydration.