Cortisol levels and 24-hour urinary free cortisol levels were tested in 72 normal controls and in 30 patients diagnosed with chronic fatigue syndrome (CFS). The research appeared in the Journal of Clinical Endocrinology and Metabolism (1991;73(6):1224-1234). The patients with CFS had lower evening cortisol levels and lower free cortisol excretion (found in 24-hour urine test).
ACTH stands for Adrenocorticotropic hormone. It stimulates the adrenal cortex to secrete cortisol (a glucocorticoid). The study found that the CFS patients had higher concentrations of ACTH. They had an overall increased sensitivity to ACTH, but a reduced maximal response to the hormone. In general, CFS patients have lower levels of glucocorticoids (like cortisol) than healthy people.
The authors of the study feel that CFS patients may have an adrenal insufficiency, which makes the adrenal glands more sensitive to ACTH. The fact that the adrenal glands do not respond as well to high doses of ACTH may indicate that there may be some atrophy of the glands (perhaps due to overstimulation).
CRH is corticotropin-releasing hormone (CRH), originally named corticotropin-releasing factor (CRF), and also called corticoliberin, is a polypeptide hormone and neurotransmitter involved in the stress response. It stimulates the pituitary to make ACTH and it is inhibited by cortisol. In CFS patients, the adrenal insufficiency may be due to a deficiency of CRH.