Cortisol Rhythm, HPA Axis Dysregulation and Why "Adrenal Fatigue" Is Contested
Level 2, Intermediate
In brief
The idea that chronic stress exhausts the adrenal glands, causing “adrenal fatigue”, was popularised in the late 1990s. Systematic review has found no consistent evidence that it exists as a distinct condition, and endocrine societies do not recognise it. Real disturbances of cortisol regulation do occur, in depression, post traumatic stress, chronic fatigue states, shift work and genuine adrenal disease, and they are driven mainly by the brain’s regulation of the HPA axis, not by glandular exhaustion. Unregulated adrenal supplements can cause harm.
An earlier article in this series introduced the stress response and explained why adrenal fatigue is not a recognised diagnosis. This article goes further. It traces where the idea came from, examines what cortisol testing can and cannot show, describes the real patterns of cortisol dysregulation that research has identified, and considers why the concept remains so popular. Understanding the debate in depth helps practitioners respond to patients who arrive convinced they have adrenal fatigue with both respect and accuracy.
Where the idea came from
The concept of adrenal insufficiency caused by stress has older roots, but the term adrenal fatigue was popularised by a 1998 book written by a chiropractor and naturopath. It proposed that prolonged stress causes the adrenal glands to become overworked and eventually unable to produce adequate cortisol, leading to fatigue, cravings, low mood, poor sleep and difficulty coping with stress. The idea spread rapidly through popular health media and parts of complementary and functional practice, along with salivary cortisol tests and adrenal support supplements.
The model borrows from genuine physiology: the HPA axis does respond to stress, and cortisol patterns do change in some chronic conditions. What it adds, the idea that the glands themselves become exhausted, is the part without evidence.
What the evidence shows
A systematic review published in 2016 examined studies that had investigated adrenal fatigue or used the concept. The authors found that the studies used inconsistent methods and definitions, that results were contradictory, and that there was no consistent evidence of adrenal fatigue as a distinct condition. They concluded that adrenal fatigue does not exist as an established entity. Endocrine societies have advised patients that adrenal fatigue is not a real medical condition and that no test can diagnose it.
The adrenal glands have a large reserve capacity. In people with genuine primary adrenal insufficiency, symptoms usually appear only after most of the adrenal cortex has been destroyed. Psychological stress has not been shown to exhaust healthy glands in this way.
Measuring cortisol: what each test can show
| Test | Validated uses | Limitations |
|---|---|---|
| Morning serum cortisol | Screening for adrenal insufficiency, often followed by stimulation testing | Single value; affected by timing, binding proteins and oral oestrogen |
| ACTH stimulation test | Diagnosing adrenal insufficiency | Specialist test |
| Late night salivary cortisol | Screening for Cushing syndrome | Validated for this specific purpose |
| 24 hour urinary free cortisol | Screening for Cushing syndrome | Affected by collection accuracy and fluid intake |
| Dexamethasone suppression test | Screening for Cushing syndrome | Affected by some medicines |
| Salivary diurnal cortisol profiles | Research into stress and health | Not validated for diagnosing adrenal fatigue or guiding treatment; affected by sampling timing, sleep and many other factors |
| Hair cortisol | Research into long term cortisol exposure | Research tool, not a clinical diagnostic test |
| Urinary cortisol and cortisone metabolite panels | Research and some specialist uses | Clinical significance of patterns in general wellness not established |
Salivary cortisol profiles show a great deal of day to day variation within the same person and are sensitive to the timing of each sample relative to waking. A single day’s profile labelled as showing adrenal fatigue cannot bear the diagnostic weight often placed on it.
Real patterns of cortisol dysregulation
Research has identified genuine differences in cortisol regulation in several conditions. Importantly, these point in different directions and reflect altered regulation by the brain rather than glandular exhaustion.
| Condition | Cortisol findings in research |
|---|---|
| Major depression, particularly melancholic | Often raised cortisol and impaired feedback suppression |
| Post traumatic stress disorder | Some studies report lower cortisol and enhanced feedback sensitivity; findings vary |
| Chronic fatigue syndrome | Some studies report mildly lower cortisol and a blunted stress response; likely a consequence as much as a cause |
| Burnout | A systematic review found no consistent biomarker, including cortisol |
| Shift work and circadian disruption | Altered timing and flattened daily rhythm |
| Chronic stress | Varied: raised, flattened or blunted patterns depending on the person and stressor |
At population level, a flatter daily cortisol slope has been associated in cohort studies with higher mortality. This supports the idea that cortisol rhythm matters for health, but it does not provide a diagnostic test for individuals.
Real adrenal disease
Genuine adrenal insufficiency is uncommon but important, and can be missed if symptoms are attributed to adrenal fatigue. Features such as weight loss, dizziness on standing, low blood pressure, salt craving, skin darkening, abdominal pain and low sodium or high potassium warrant urgent medical assessment. A common cause of secondary adrenal insufficiency is stopping long term glucocorticoid treatment, including high dose inhaled or topical steroids in some people, which is why steroids should be tapered under medical guidance.
The danger of adrenal support supplements
Many over the counter adrenal support products contain glandular extracts. A laboratory analysis of such products found that many contained thyroid hormone and some contained steroid hormones, including cortisol related compounds, which were not always declared. Taking undeclared steroids can suppress the body’s own adrenal function, so that stopping the product precipitates genuine adrenal insufficiency. Prescribing hydrocortisone for adrenal fatigue carries the same risk. These are real harms arising from treatment of a condition that has not been shown to exist.
Why the concept persists
- It gives a name and a biological explanation to real, distressing symptoms that conventional care may have dismissed.
- It validates the patient’s experience that stress has affected their body, which is true.
- It offers a clear treatment path.
- Its recommended lifestyle changes, better sleep, reduced caffeine, regular meals and stress reduction, often help, reinforcing belief in the diagnosis.
Understanding these reasons allows practitioners to meet the underlying needs without endorsing the label.
A better conversation
When a patient arrives with a diagnosis of adrenal fatigue, a respectful approach might include:
- Acknowledging that their symptoms are real and that stress affects the body profoundly.
- Explaining that the adrenal glands do not appear to become exhausted by stress, and that the tests used to diagnose adrenal fatigue are not reliable.
- Assessing properly for conditions that cause similar symptoms: anaemia, iron and B12 deficiency, thyroid disease, sleep apnoea, depression, perimenopause and, where features suggest it, genuine adrenal disease.
- Reviewing any adrenal supplements or steroids and arranging safe withdrawal where needed, with medical input.
- Addressing the real mediators: sleep, workload, caring responsibilities, mood, activity and nutrition.
- Offering a new explanation: chronic stress with disrupted sleep and HPA axis regulation, which is real, understandable and responsive to change.
An illustrative case
A 39 year old manager has been taking an adrenal support supplement for 8 months after a salivary profile labelled her with stage 3 adrenal fatigue. She wants to stop it but feels worse whenever she misses a dose. Her doctor, suspecting steroid content, checks a morning cortisol while she continues the product; it is unexpectedly low, suggesting suppression. The product is withdrawn gradually under medical supervision with appropriate monitoring. Meanwhile her fatigue is assessed: her ferritin is low and she sleeps 5 hours a night during a stressful period at work. Iron replacement, a protected sleep schedule and support with workload follow. Over several months her energy recovers. The supplement had been causing a real adrenal problem while the actual causes of her fatigue went unaddressed.
Taking stress seriously, accurately
Rejecting the concept of adrenal fatigue is not the same as dismissing stress or the patient. Stress genuinely changes physiology, including cortisol regulation, and it genuinely makes people unwell. Describing it accurately protects patients from unreliable tests and harmful supplements, and directs attention to the causes and treatments that actually help.
Questions about adrenal fatigue
Is adrenal fatigue real?
Can salivary cortisol tests diagnose adrenal fatigue?
Are adrenal support supplements safe?
References
- Cadegiani FA, Kater CE. Adrenal fatigue does not exist: a systematic review. BMC Endocrine Disorders. 2016;16(1).
- Kaur RJ, Kumar M, Saini R, et al. Over the counter adrenal support supplements contain thyroid and steroid based adrenal hormones. Mayo Clinic Proceedings. 2018;93(3).
- Kumari M, Shipley M, Stafford M, Kivimaki M. Association of diurnal patterns in salivary cortisol with all cause and cardiovascular mortality: findings from the Whitehall II study. Journal of Clinical Endocrinology and Metabolism. 2011;96(5).
- Biomarkers in burnout: a systematic review. Journal of Psychosomatic Research. 2011;70(6).
- Bornstein SR, Allolio B, Arlt W, et al. Diagnosis and treatment of primary adrenal insufficiency: an Endocrine Society clinical practice guideline. Journal of Clinical Endocrinology and Metabolism. 2016;101(2).
- Nieman LK, Biller BMK, Findling JW, et al. The diagnosis of Cushing’s syndrome: an Endocrine Society clinical practice guideline. Journal of Clinical Endocrinology and Metabolism. 2008;93(5).
Continue your learning
Investigating fatigue with rigour
Stress and its physiology, and how to talk with patients about it accurately, are taught in the Health Coaching and Stress Management module of IIFM’s 6 month Functional Medicine and Clinical Nutrition program.
This article is for the education of healthcare professionals. It is not a substitute for individual medical advice, diagnosis or treatment, and does not change any practitioner’s scope of practice. Regulation and guidelines differ between countries.