Studies of the hypothalamo-pituitary adrenal (HPA) axis in chronic fatigue syndrome show a mild hypocortisolism of central origin, in contrast to the hypercortisolism of major depression…In some patients with chronic fatigue syndrome, low-dose hydrocortisone reduces fatigue levels in the short term. Treatment for a longer time and follow-up studies are needed to find out whether this effect could be clinically useful.