Cortisol
The main stress hormone — essential for short-term survival, but problematic when chronically elevated.
Table of contents
TL;DR
The main stress hormone — essential for short-term survival, but problematic when chronically elevated.
- →A normal cortisol rhythm supports morning wakefulness and energy metabolism
- →Plays a key role in the acute stress response and inflammation regulation
- →Essential for proper regulation of blood pressure and water-electrolyte balance
| Hormone type / class | Glucocorticoid (steroid hormone) |
|---|---|
| Where it's produced | Adrenal cortex, under control of the hypothalamic-pituitary-adrenal (HPA) axis |
| Evidence level | Strong — well-documented physiology and circadian rhythm |
| Natural circadian rhythm | Peak 30–45 min after waking (CAR), decline to a minimum around midnight |
| Measurement method | Blood, saliva (diurnal profile) or hair (long-term exposure) |
| Status | Endogenous hormone — not a supplement, not subject to dosing |
Understand
Overview
Cortisol is a glucocorticoid secreted by the adrenal cortex under the control of the hypothalamic-pituitary-adrenal (HPA) axis. It's often called the 'stress hormone,' though that's a considerable simplification — cortisol plays a key role in regulating metabolism, blood pressure, immune response and the wake-sleep cycle even under conditions of zero stress.
It shows a pronounced natural circadian rhythm — the highest level occurs 30–45 minutes after waking (the so-called cortisol awakening response, CAR), gradually falls throughout the day, and reaches its lowest point around midnight. This rhythm is one of the pillars of human chronobiology and is disrupted by, among other things, shift work, jet lag and chronic sleep deprivation.
Because cortisol is an endogenous hormone rather than a substance you take, the question 'who is it good for' doesn't quite apply — it's more a matter of whose cortisol rhythm is worth observing and supporting. This applies especially to people with chronic stress, shift workers, and those dealing with jet lag or prolonged sleep deprivation — in these groups a disrupted circadian cortisol rhythm is linked to worse sleep quality, increased visceral fat gain and weakened immunity. On the other hand, a brief, acute rise in cortisol in response to a real stressor (an exam, a workout, a threat) is a normal, adaptive physiological response, not something that needs to be 'treated' or lowered. People who suspect significant HPA axis dysregulation (e.g. symptoms of Cushing's syndrome or adrenal insufficiency) need medical evaluation, not self-interpretation of test results or self-supplementation.
History of use
Cortisol (hydrocortisone) was isolated in the 1930s and 1940s by the teams of Edward Kendall and Tadeusz Reichstein, and its anti-inflammatory clinical effect was described by Philip Hench — these discoveries were honored with the Nobel Prize in Physiology or Medicine in 1950. Since then, research on cortisol has evolved from anti-inflammatory pharmacology to modern psychoneuroendocrinology, which studies, among other things, the relationship between psychosocial stress and this hormone's circadian rhythm.
Mechanism of action
In response to stress (physical or psychological), the hypothalamus releases corticotropin-releasing hormone (CRH), stimulating the pituitary gland to secrete ACTH (adrenocorticotropic hormone), which in turn triggers the adrenal cortex to produce cortisol. The hormone mobilizes glucose from liver stores (gluconeogenesis), modulates the immune response (at high concentrations it acts as an anti-inflammatory and immunosuppressant), and affects wakefulness through interaction with the noradrenergic system.
This system operates on a negative feedback principle — elevated blood cortisol inhibits further release of CRH from the hypothalamus and ACTH from the pituitary, which under normal conditions prevents an excessive, chronic rise in the hormone. The circadian rhythm of cortisol is governed by the body's biological clock, located in the suprachiasmatic nucleus of the hypothalamus (SCN), which synchronizes the HPA axis with the light-dark cycle. Cortisol acts on target tissues via two types of receptors — the glucocorticoid receptor (GR), present in nearly all cells of the body, and the mineralocorticoid receptor (MR), which has higher affinity and is involved, among other things, in regulating water-electrolyte balance. It's chronic overload of this feedback system — not a single stressful episode — that underlies the negative health effects described in the literature.
Stress trigger
A physical or psychological stressor prompts the hypothalamus to release corticotropin-releasing hormone (CRH).
Pituitary stimulation
CRH stimulates the pituitary gland to release ACTH (adrenocorticotropic hormone) into the bloodstream.
Adrenal production
ACTH stimulates the adrenal cortex to synthesize and secrete cortisol.
Peripheral effects
Cortisol mobilizes glucose from the liver, modulates the immune response and affects wakefulness.
Negative feedback
Elevated cortisol inhibits further release of CRH and ACTH, limiting its own production.
Evidence: strong — based on 2 studies in this database.
Benefits
Practice
Frequently asked questions
The best-documented interventions are improving sleep quality, regular moderate-intensity physical activity, stress-reduction techniques (e.g. meditation), and cutting back on excessive caffeine intake.
A brief rise in cortisol in response to a stressor is a normal, adaptive physiological response. The problem is chronic, long-term elevation resulting from ongoing stress, lack of sleep, or certain conditions (e.g. Cushing's syndrome), which is linked to negative metabolic and immunological consequences.
The most common methods are a blood test (a single time point, usually in the morning), a diurnal profile from saliva samples taken several times a day, or hair cortisol analysis, which reflects average exposure over the past several months.
Dosage & timing
Typical dose
Not applicable — this entry describes an endogenous hormone, not a substance for supplementation
Form
—
Cortisol levels are assessed through a blood test, saliva (diurnal profile), or hair analysis (long-term cortisol exposure).
Best times to take it
- Natural peak 30–45 minutes after waking (the so-called cortisol awakening response)
Safety
Side effects & contraindications
Possible side effects
Chronically elevated cortisol is associated with sleep disturbances, increased visceral fat gain and weakened immunity
Contraindications
Not applicable — cortisol is an endogenous hormone, not a supplement
Interactions
Many medications and substances (caffeine, alcohol, sleep deprivation) affect its secretion
Is it worth taking?
Who it's for
- A normal cortisol rhythm supports morning wakefulness and energy metabolism
- Plays a key role in the acute stress response and inflammation regulation
- Essential for proper regulation of blood pressure and water-electrolyte balance
Not for
- Not applicable — cortisol is an endogenous hormone, not a supplement
Evidence
Studies
The level of psychosocial stress is systematically associated with the magnitude of the morning cortisol awakening response.
Chida Y, Steptoe A., Biological Psychology, 2009
Cortisol awakening response and psychosocial factors: a systematic review
Strong evidenceChida Y, Steptoe A. · Biological Psychology · 2009
A systematic review describing the relationship between psychosocial stress levels and the cortisol response after waking.
View studyChronic stress, cortisol dysfunction, and pain: a psychoneuroendocrine rationale
Moderate evidenceHannibal KE, Bishop MD. · Physical Therapy · 2014
A review describing the consequences of chronic HPA axis dysregulation, including its effect on pain perception and inflammation.
View studySources & bibliography
Citations are illustrative for this demo version and require full bibliographic verification by the editorial team before production publication.
Compare with similar entries
About the authors of this entry
Author
dr Piotr ZielińskiEndocrinologist
Piotr reviews content on hormones, metabolic health and supplement pharmacology.
131 publications on this site
Medical review
dr Anna KowalczykEditor-in-Chief, Molecular Biology
Anna oversees the editorial process and scientific review of every publication in the knowledge base. She previously researched autophagy and mitochondrial biology.
50 publications on this site
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Comments (2)
- KW
Kasia W. 2 weeks ago
Very clearly explained, especially the interactions section — I hadn't seen it laid out this well anywhere else.
- MT
Marek T. a month ago
Are you planning to update this with the newest study from this year? I saw an interesting meta-analysis.