My husband has this and we have been revisiting James L Wilson's book on Adrenal Fatigue, what he calls Hypoadrenia. ( For reference- https://www.amazon.co.uk/Adrenal-Fatigue-Century-Stress-Syndrome/dp/1890572152) When husband had an adrenal saliva test, we was at rock bottom in 2008. NHS Synacthen test showed nothing. The short Synacthen test is a test of adrenal insufficiency (oh no it doesn't!) which can be used as a screening procedure in the non-critically ill patient. (balderdash!) The test is based on the measurement of serum cortisol before and after an injection of synthetic ACTH (also known as tetracosactrin).