Hi Sandra,

I don't know if this will answer your questions, either.  Let me start by saying that I have little, to no, first-hand experience with renin values---we have only run the renin test once, and that was when my son was first diagnosed.  So what little I know is only from what I've read and what I've deduced, so pls. keep that in mind.

First, the difference between a salt-waster and a simple virilizer is that a salt-waster has high renin and deficient aldosterone; while a simple virilizer only has high renin, but normal aldosterone.  That much I know is a fact.  From that fact---and to answer the first part of your question---I would deduce that a simple-virilizer, such as your son, could have high renin values, but normal electrolytes, since aldosterone is what governs the fluid and electrolyte balance in the body, and aldosterone is not deficient in simple-virilizers.  (As I said, though, this is what I would conclude based on my limited reading on the subject---it is not a question I have asked point-blank of my doctor.)

As to your other question regarding the stability of the renin test and whether you need to worry about having to run it again---my guess is no, you do not need to worry that the number was inaccurate.  However,  this is, again, just what I've deduced by looking at charts of normal renin values and based on our own experience, and this is what has led me to those conclusions:

First, when looking at the charts, I see that there is a very wide range of normal renin values, especially in the early years (see table below).  I am wondering if that is what your doctors mean by the variability of the test---rather than the fact that it might change into a whole different range, if you took it on another day.  It does look like different ranges are given for upright vs. supine positions, but it looks like "normal" has already been adjusted to take that into account.

Second, from personal experience: As I mentioned, we've only run renin once, period.  (It was not elevated, and my son was determined not to need florinef.) If it was a very variable and fluctuating number, I am sure our doctor would check it more frequently, but he obviously has not seen the need, since we did it that first time.  How do I know he is not overlooking something? Mostly through past experience with him---over time I have developed a huge amount of confidence in him and discovered that he always has a good reason for doing, or not doing, something---and he is always right!  So, in our case, at least, I am not at all afraid that something has been "missed" as a result of our not ever having repeated this test, and I am quite comfortable in concluding that---unlike something like 17-OHP or cortisol---renin is a fairly reliable number.

Despite the difference in classification---and the difference of normal vs. abnormal aldosterone secretion----I think the important thing to keep in mind is that the treatment of simple-virlizers and salt-wasting CAH patients is exactly the same, i.e. both take florinef and hydrocortisone replacement to treat the CAH.  Routinely checking renin levels in both these types of patients is important in order to assess the adequacy of the florinef doseage.  In that way, then---and to answer your third question---I guess I would have to go with the opinion of the first doctor, who thought your son's florinef should be increased because of a high renin value.  On the other hand, if your son's renin number was on the high end of normal, but still normal, perhaps your doctor is justified in making no changes to his meds, at this time.  Either way, if renin was the only questionable number, it doesn't seem as if there was any reason to double the cortef, as the nurse on the phone told you to do.  In that respect, I think you were right not to make any changes to your son's medication regimen, until you spoke directly to your own doctor, especially if the instructions didn't make sense to you. 

So, has that just served to confuse the issue even further??  I am not trying to be an armchair physician, merely trying to help put things in a context where you can formulate the right questions to ask your doctor, in order to feel completely satisfied with the course of your son's treatment.  As I said earlier, I have little to no personal experience with renin, so please take what you need and feel free to discard the rest. 

P. S.  So glad to hear your other two boys came back "normal".....Congratulations!!

P. P. S.  For some reason, when I try to paste in the chart I was talking about,  the data completely disappears...I have no idea why.  So I will merely retype what it gives as normal for a child your son's age:  Between 1-12 months old: 235-3700 ng/dl/hr (mean 1170).