It depends where the blood is being taken.  Before meds or after meds?  Possibly the reason levels of 17 OHP may seem low is you had bloods taken after she has had her morning meds?  (I hope it wasn’t before her morning med’s anyway because that would mean the 10pm dose is over suppressing--and she would certainly not be growing).  This means cortisol levels are quite high and 17 OHP levels in contrast to that will be very low.  If you took the blood tests just before the tablets were taken you’d have an accurate example of what her 17 OHP had elevated to since the latest PM dose and this would then be expected to fall within the 500-1000 ng/dl ranges.  However, because some people take their meds before the blood tests, the meds interfere with the results and can make for varying results.  For example, if you take blood 1 hr after the dose, then levels would be very low for 17 OHP if at all traceable in some kids.  If it were 2 hours after then the 17 OHP levels may be a little higher than they had been when taken the hour before because the cortisol levels are lowering and the 17 OHP starts to rise.    Likewise taking 3 hr’s after the dose would result in even higher 17 OHP levels.  This is how the med’s affect the blood tests results. 

Since cortisol suppresses 17 OHP, and when levels fall lower 17 OHP is released more prolifically, it’s like a see saw effect.  In a sense I feel that it’s far better taking bloods before med’s.  Our Doctor used to take it in the afternoon, morning, mid morning--he was sooo erratic!  He had no qualms whatsoever about varying the times in the day that bloods were drawn, so goodness knows how he could ever have any accuracy or consistency in the results.  You need to beware of any Doctor that doesn’t mind when the bloods are taken because it was not a good time for us or Ashley when this happened. 

I asked him lot’s of times and he once told me it didn’t matter as they factored all this in---goodness knows what factoring he was using or theory here---it’s not as if he was an Endocrinologist even just a Paed.  The end result?  A total mess where bone age and growth is concerned and not a very accurate control of Ashley’s CAH that’s for sure.    To my mind why bother to taking bloods at all if your not going to even be consistent with where you take them or look at what the true levels are just before the child takes their next dose?  After all, we do want to know that the last dose actually was the right dose don’t we?  So why give another dose until you have measured the 17 OHP in the blood just to be sure what it is elevating too before the next dose is given?  That way you can atleast see if they exceeded the 50nmol/L or 1000 ng/dl ranges?  How could you see that if you taint the results with more cortisone tablet or meds?  The whole point of the exercise should be to measure the levels of 17 OHP in the blood before the next dose is taken to make sure that the last dose did what it was supposed to do and that the 17 OHP fell within the recommended ranges of 500-1000 ng/dl.  Ranges that have been used and shown in studies to be the correct range to achieve a good steady rate of growth in CAH children.  If you do it the other way around, and take bloods after the morning meds, where are the studies regarding the official ranges that they are supposed to use?  Have any been published?  To be honest I don’t think so. 

You could not possibly use the 500-1000 ng/dl surely as those ranges are based on children whose blood is taken before meds are given first thing in the morning surely for the most part?  I assume this only because if your child is still growing and her 17 OHP levels are almost undetectable, then the normal ranges for children whose bloods are drawn after the meds are given certainly have to be around 200 ng/dl and under?  Depending of course upon how long after the dose the bloods were taken.  

Thats why  asume that the 500-1000 ng/dl ranges are taken mainly as a target for those that have had blood tests befor their morning meds are given.    Being that they are far higher than normal childrens 17 OHP levels at that time, this would atleast make sense.   Normal children’s levels are detectable from what I can gather so a child who has had a large dose of cortisone would certainly have levels way under the normal 17 OHP ranges.  I just find it sad when they do this because they are just using growth as an indicator (which can cause delay in picking up any problems for over three months if they don’t check this right and assess it right).  Thats because they are not checking if the child is well covered or over treated by assessing the efficacy of the dose.  I.e.  the 10pm dose which is mant to last a child up to their am dose at around 7-8am.