“Adrenal fatigue” is not a thing
Adrenal fatigue was invented by a chiro so he could sell a cure. It is supposedly caused by chronic stress and “burnout” of the adrenal glands, and it’s a common bogus explanation (see Cadegiani et al) for fibromyalgia and chronic widespread pain. At best, that’s a simplistic guess; at worst, it’s a great way to peddle false hope to fibromyalgia patients.