Adrenal insufficieny with normal acth test??

Hi all,
I've been a regular on the Dysautonomia forum with Postural Orthastatic Tachycardia Syndrome.  I think before I get in to a ton of questions I should see if I'm even in the right place.  I've had a 24 saliva test and then a 24 hour urine test which both showed low cortisol levels but then I had the acth stimulation test which turned out to be completely normal.  Is it possible to still have some kind of adrenal or endocrine issue with a normal acth test? I keep thinking the low cortisol levels must mean something.  Anyone have any thoughts that might help here? My endocrinologist seemed at a loss and I want to make sure that I'm not missing anything.
Thanks so much for any help you can offer!!!
-Lala

[rumpled]

Unfortunately, testing cortisol is part art and part science. You tested 2 days if I get your testing correctly - the saliva test covered one day and the urine another? That is not a lot of testing. Was it serum cortisol that was low in the morning? Have you had serum cortisol testing as well? Free cortisol can be interfered by medications and other things so it pays to test a lot to see the entire adrenal (were other hormones tested) and see what is up.
Is your sodium and potassium normal? The POTS could be related to an issue with them - were renin and aldosterone tested?

[crawlerBug]

Ask for the Insulin stress test, which will also test your CRH response, which stimulates ACTH.

[LaLa4]

Thank you both for your comments, I just emailed my endocrinologist with your responses to see what he thinks.  I'm sure the POTS is related and I've spent over a decade trying to figure this out and hopefully some day someone will figure it out and I'll get some relief!!

[rumpled]

Make sure you get copies of all your tests!