It is my understanding that if a renin (PRA) result is low, it shows the control is good regarding the mineralocorticoid side of things, if the renin level is high, then it would show the kidneys are leaking salt, so either more fludrocortisone is needed, or more salt needs to be consumed.  This is why some babies need a lot of fludro/salt as their kidneys tend to leak more salt when they are immature, and as they mature the fludro dose is sometimes reduced.

 

MR I would guess that your daughter’s renin is low, because there are mineralocorticoid  properties in hydrocortisone (none in dex)

 

As for the 17 OHP, it seems that the doctors these days, tend to look at the androstenedione level as this shows a 24 hour picture of control, where are the 17 OHP only shows a snap shot view at that moment.  I still think a series of 17 OHP levels thoughout the day, before a each dose the most useful as then it can help fine tune the medication as to what time and how much each dose should be. In the UK some centres do this by using blood spot cards at home which are sent to the labs. To be honest it would be good if the doctors could really all agree on a protocol but I guess with CAH being such an individual disorder, it would be difficult.