I have one more clarification/correction to Val’s post.

“Therefore what this study proves is that no matter WHAT dose of Hydrocortisone is given---high or low---it is ALL secreted out at the same time.  In other words it does not last any longer in some children than it does in others.  Also it proves that even if you gave 20mg of Hydrocortisone, it would ALL be out of the blood serum exactly 6-7 hours after secretion. “

Val, the study actually gives wide ranges for these values.  The morning dose reached undetectable concentrations after a median time of 7 hours, but the range was 5-12 hours.  The evening dose reached undetectable levels at a median time of 9 hours, also with a range of 5-12 hours.  This would account for the fact that some children seem to have adequate coverage remaining from the bedtime dose, and some do not.

This data does not negate the theory that large bedtime doses of HC are problematic.  I agree with you completely there. 

BTW, I love the thermostat/radiator analogy.  I’d never thought of it that way.  It’s a good one to use when explaining CAH to the kids.