I do think that 17 ohp is too high.  We always keep our daughter under 500.  Right now however she is 11,000 so the endo just increased her from 17.5 mg a day to 22.5 mg a day.  I am sure this will lower the 17 ohp back to normal levels.  She is almost 11 and has grown alot in the past year.  Tests were a tiny bit high the last time ( a couple months ago) but we decided to wait until next test to see if it was still high.  It was way high (the 11,000).  Dont take chances with that.  Does your endo want to raise the cortef?