Hi! Is your body very flexible? Hyperflexable joints? There is an association with POTS and many people with Joint Hyperflexability Syndrome/Ehlers-Danlos Type III.
If you think this might be a possiblity, a geneticist is best to confirm.
My son has POTS, Joint Hyperflexability and extremely low aldosterone with normal renin. Apparently, this is a common finding in many POTS patients.
Do you have any gastrointestinal symptoms, digestive problems or acid reflux, for instance?
Did they rule out Addison's then, since your aldosterone was abnormal? Did they look at your iron and ferritin (iron stores), TIBC (total iron binding capacity) and iron saturation percentage since your RBCs came back abnormal? Mine were low recently while at the hospital. Previously, when they were low, my ferritin was low. Iron deficiency can cause rapid heart rate. So even if you have POTS, it can make you worse. If they haven't checked on these things, I hope you can get them to!
The electrophysiologist who diagnosed me with POTS told me it was hereditary and usually comes out in the third decade of life or something like that. I later learned I have a second cousin who was also diagnosed with it.