Cortisol levels and 24-hour urinary free cortisol were measured in 72 healthy controls and 30 patients diagnosed with chronic fatigue syndrome (CFS). The research appeared in the Journal of Clinical Endocrinology and Metabolism (1991;73(6):1224–1234). Patients with CFS had lower evening cortisol levels and reduced free cortisol excretion, as measured by 24-hour urine testing.
ACTH (adrenocorticotropic hormone) stimulates the adrenal cortex to secrete cortisol, a glucocorticoid. The study found that patients with CFS had higher concentrations of ACTH. They also demonstrated increased sensitivity to ACTH, but a reduced maximal response to the hormone. Overall, CFS patients tend to have lower levels of glucocorticoids, such as cortisol, compared to healthy individuals.
The authors suggested that patients with CFS may have a form of adrenal insufficiency that makes the adrenal glands more sensitive to ACTH. The diminished response to high doses of ACTH may indicate some degree of adrenal atrophy, possibly due to chronic overstimulation.
CRH (corticotropin-releasing hormone), originally called corticotropin-releasing factor (CRF) and also known as corticoliberin, is a polypeptide hormone and neurotransmitter involved in the stress response. CRH stimulates the pituitary gland to produce ACTH and is inhibited by cortisol through negative feedback. In patients with CFS, adrenal insufficiency may be related to impaired CRH signaling.
