I have found myself, surprisingly unlike most other sufferers of "Adrenal Fatigue" (or some issue that presents similarly) that I have seen in this forum, to be very interested in the mechanisms involved. That is, for example, if I find I have sore joints or afternoon fatigue or a feeling of suffocation, I want to know how that's happening in my body to produce those symptoms. Are the joints sore because of inflammation? What kind of inflammation is it and what might be causing it? I figure the more I can understand what's going on to cause the symptoms the better I can figure out what's causing all of the symptoms, the better I can get at the root and cure the issue once and for all.
So, shortness of breath... Here's one possible route that jibes with other problems I've been having:
Digestive issues or problematic GI tract can result in B12 deficiency. Deficiency of B12 can result in a kind of anemia (deficiency of red blood cells) called "megaloblastic anemia". A deficiency of red blood cells can result in shortness of breath. So, poor absorption of B12 can lead to shortness of breath.
So here's another AF symptom that has something to do with digestion problems.