17-OHP is a stress hormone....and I have looooong complained about the wisdom of checking the stress hormone level of a child who is crying and upset and definitely does NOT want to have blood drawn. "gee...their 17-OHP levels are high"...yeah...no kidding. However, it's one of the better marker steroids to use. Androstenedione is a test to run with it....maybe even testosterone...to check for potential discrepancies before making a dosage adjustment. 17-OHP is, perhaps, a good diagnostic tool to determine IF your child has CAH....but maybe not good enough for a maintenance tool. Is your child a salt-waster? If so, plasma renin should probably be checked routinely. A non-SW doesn't really need the renin checked. Once a non-SW; always a non-SW....and vice-versa. There's either a block in that enzymatic pathway or there isn't.