louise, the greatest peak of cortisol and therefore 17ohp is at 3am and continues until the morning.  there is also a fair level from late morning until approx 6-7pm.  from that time until 3am there are very low levels.   hydrocortisone kicks in in about 1 hr after the dose is given and works approx 6hrs.  therefor the highest doses should be late at night or in early morning with smaller doses in the early evening.  you need to have better communication with your endo if he did not make it clear what your dosing schedule should be.  be persistent and make him spend the time with you as he should.  I am not an expert but this is what i have learned from researching my daughters swcah.  good luck to you and your children.