Adrenal fatigue (or insufficiency) can be caused by chronic pain, other forms of stress, infection, inflammation, environmental toxins, diet (caffeine, carbohydrates) and other factors - not just opioids. It's often found in people with diabetes and thyroid problems.
Google: adrenal fatigue causes

If you suspect some particular reason/trigger, try googling that with adrenal fatigue, and see if a cause/effect connection turns up in the literature.

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