Fatigue that improves with caffeine (as it forces increased cortisol secretion) or hydrocortisone intake may suggest transient (reversible) hypoadrenalism due to excess cortisol requirement. Unfortunately, hypoadrenalism is difficult to detect in blood work and is often normal even in patients with who are severely ill, unless suffering from pituitary or supradrenal tumors, etc.
One of the most important causes of reversible adrenal exertion symptoms in patients with chronic pain, is TOS CVH. TOS CVH causes high arterial brain pressures that lead to paradoxical systemic hypotension due to cerebral autoregulation. This will raise adrenal output to perform daily tasks, ie. raise blood pressure and cardiac output through the sympathetic system, often resulting in profound fatigue, and as a worst case scenario, myalgic encephalomyelitis, if it goes on over a longer period of time. Usually, years.
Patients who have fatigue that responds to caffine but who do not have chronic pain, should mainly look to their sleep, diet and training habits. If sleep and diet is ok, then cardiovascular health is perhaps the most important aspect. Poor cardiac compliance to physical stressors, ie. inadequate strength of the heart, will be compensated for by a raised sympathetic tone and raised adrenal output. Increasing sodium intake can also help, but this should not be done excessively, as the heart may not tolerate a greater blood volume until its strength has been increased. This patient group should stick to [no more than] one cup of coffee per day, preferably in the morning and avoiding high-carbohydrate meals in the evenings. Mental stress also influences, needless to say.
A good indication of improved heart strength is reduced resting heart rates, but also overall lower heart rates during activities. Training too hard too often will strain the adrenal system and make the problem worse than it was initially, so starting with a 45-minute brisk walk once to twice per week, then gradually "feel it out from there", can be appropriate.
