Cortisol

Cortisol is a steroid hormone released by the adrenal glands which sit upon the kidneys. Release of cortisol is controlled by the hypothalamus, a part of the brain. Cortisol has several known roles in the human body: aiding in metabolism, reducing inflammation, assisting electrolyte balance, stimulating gastric-acid secretion and controlling one's sleep/wake cycle.

Normal blood level of cortisol vary throughout the day, with the highest level in the morning upon awakening and lowest level around midnight. Levels can also rise in reaction to stress or low blood sugar. Some health conditions can cause an increase in cortisol, such as depression and Cushing syndrome. Other health conditions can cause a decrease, such as Addison’s Disease and ME/CFS.

ME/CFS
Hypocortisolism (a low cortisol level) frequently occurs in patients with ME/CFS, confirmed by studies measuring cortisol levels and in urine and saliva.

In addition to general hypocortisolism, ME/CFS patients have a decreased cortisol awakening response, ie, morning cortisol levels peak later compared to healthy controls.

In 2018, Roerink, et al, studied hair cortisol concentrations in CFS patients to assess if hypocortisolism was a prolonged phenomenon. They found that there was a trend of lower hair cortisol concentrations in CFS patients, thus suggesting that hypocortisolism was long-term in ME/CFS.

As people with ME/CFS improved, their hypocortisolism improved.

Notable studies

 * 2018, Hair and salivary cortisol in a cohort of women with chronic fatigue syndrome (Abstract)
 * 2015, Salivary cortisol responses to household tasks among couples with unexplained chronic fatigue (Full Text)
 * 2014, The role of hypocortisolism in chronic fatigue syndrome (Abstract)
 * 2000, Review article - Chronic Fatigue Syndrome: A Dysfunction of the Hypothalamic-Pituitary-Adrenal Axis (Abstract)
 * 1998, Urinary free cortisol excretion in chronic fatigue syndrome, major depression and in healthy volunteers (Abstract)

Learn more

 * Wikipedia - Cortisol
 * All You Need to Know About Cortisol and Its Health Effects
 * The Cortisol, PEM and Stress Management Link in Chronic Fatigue Syndrome by Cort Johnson in Health Rising