We’re not sure.  It has happened twice with our older son who is 3 & both those times seemed to be related to not eating much the day before.  I think it may have been the same with our 1 year old this time.  He didn’t eat much for snack time, the same for dinner (he’s teething), and it didn’t occur to me that it really wasn’t enough until the morning when I went to get him & he couldn’t even keep his eyes open.  We’ve talked to our endo about this in the past & he said that if we thought they hadn’t eaten enough, we should double their cortef at the 11pm dose to give them a bit extra.  With our 3 year old, when this happened, both time he got sick w/a cold or virus 2 days later.  This time with our 1 year old, we filled him full of fruits & veggies, and fingers crossed, but 3 days later he doesn’t have anything else going on.  He is teething, but I’d hate to think that caused it.  OUr endo also said if it kept occuring, we should get a glucometer.  We’ve really been on top of our 3 year old to mae sure he’s eating regularly & haven’t had a problem with him in over a year.  Apparently, we’ll need to do the same with our younger son.  It is definitely an issue for some of our CAH kids, as I’ve seen others post here about it too.  Best wishes.