This is Week 2 of our May fatigue series. Last week we covered the full medical workup for fatigue- the tests, the diagnoses, and what deserves investigation. This week we’re zooming in on one of the most misrepresented topics in the fatigue conversation: cortisol.

If you’ve ever been told your adrenals are “burned out,” been offered a salivary cortisol test, or found yourself deep in a rabbit hole of “adrenal support” supplements then this one is for you.

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Let’s Start With What Cortisol Actually Does

Before we can talk about what’s being said about cortisol online and why most of it misses the mark, it helps to understand what cortisol actually is and what it does in your body.

Cortisol is a glucocorticoid hormone produced by the adrenal cortex, the outer layer of your adrenal glands, which sit just above your kidneys. It’s regulated by the hypothalamic-pituitary-adrenal axis or the HPA axis,a feedback loop involving your brain and your hormonal system that is exquisitely sensitive to context.

Cortisol is not a villain. It is essential. It regulates your stress response, your sleep-wake cycle, blood sugar, blood pressure, and immune function. It rises naturally in the morning spiking by 38 to 70 percent within the first 30 minutes of waking as part of what’s called the Cortisol Awakening Response and gradually declines throughout the day. It pulses. It fluctuates. It responds to everything from exercise to illness to a stressful conversation.

That variability is important, and we’ll come back to it.

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Where “Adrenal Fatigue” Came From

The term “adrenal fatigue” was popularized by a book published in 2001 by a naturopath. The premise goes something like this: chronic, ongoing stress eventually overworks the adrenal glands to the point where they can no longer keep up with the body’s demand for cortisol. The result, according to proponents, is a cluster of symptoms including fatigue, brain fog, difficulty waking up in the morning, salt cravings, low mood, and poor stress tolerance.

It is a compelling narrative. It is also not supported by the evidence.

Here is the problem with the physiological premise: when you are stressed, your adrenal glands produce more cortisol, not less. That is how the HPA axis is designed. Stress activates the system. The idea that the adrenal glands gradually exhaust themselves and begin underproducing cortisol in response to the ordinary demands of modern life is not consistent with how adrenal physiology works.

The Endocrine Society which is the largest endocrinology organization in the world, representing more than 18,000 endocrinologists, has been explicit: adrenal fatigue is not a recognized medical diagnosis. There are no scientific facts to support the theory that long-term mental, emotional, or physical stress drains the adrenal glands and causes them to fail.

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What the Research Actually Shows

In 2016, researchers at the Federal University of São Paulo conducted a systematic review published in BMC Endocrine Disorders that remains the most comprehensive evaluation of the adrenal fatigue literature to date.

They searched PubMed, MEDLINE, and Cochrane which are the gold standard medical databases using every relevant search term and identified 58 studies that examined the relationship between cortisol and fatigue or burnout status. Their findings are worth sitting with.

Across those 58 studies, the results were almost entirely conflicting.

The most commonly used testing method was the Cortisol Awakening Response — measuring cortisol immediately upon waking and again 30 minutes later. Of the 27 studies using this method, more than half showed a completely normal cortisol response in fatigued subjects. Some studies found lower cortisol in fatigued patients. Others found higher cortisol. Others found no meaningful difference at all.

Studies using stimulation testing- in which a synthetic hormone is administered and cortisol response is measured found paradoxically higher cortisol in some fatigued subjects, directly contradicting the adrenal fatigue hypothesis.

The authors’ conclusion was clear: “There is no substantiation that adrenal fatigue is an actual medical condition. Therefore, adrenal fatigue is still a myth.”

Their secondary conclusions are equally important for the conversation happening online: cortisol profile tests should not be used to justify corticosteroid treatment, and cortisol profile tests have no validated clinical utility for evaluating patients with fatigue.

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The 2024 Update

In 2024, the Journal of the Endocrine Society published a paper by Hamrahian and colleagues that introduced language that I think is worth knowing: pseudo-endocrine disorders.

These are conditions that have never been scientifically proven to exist but are widely promoted in popular media, online, and through alternative and integrative medicine practitioners. Adrenal fatigue was named explicitly as an pseudo-endocrine condition that can cause real harm: it delays an accurate diagnosis, leads to unnecessary testing, and in some cases leads to treatments that are genuinely dangerous.

The paper makes clear that salivary cortisol profiles which are the home kits frequently marketed for “adrenal health” have never been scientifically validated as tools to assess HPA axis function. A result from one of these kits is not a diagnosis. It is not even a reliable data point in the context of fatigue evaluation.

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The Problem with Random Cortisol Testing

Cortisol is not a static number. It is pulsatile meaning it releases in bursts throughout the day. It is diurnal and it follows a predictable daily rhythm. It is context-dependent, it responds to stress, sleep, illness, exercise, what you ate, and what time you woke up. It is affected by whether you are on oral contraceptives or estrogen therapy, which alter cortisol-binding globulin levels and can change how a serum cortisol is interpreted.

The Endocrine Society guidelines are explicit on this point: there is no evidence to support the use of random cortisol to rule out adrenal insufficiency. A single cortisol level drawn at an unspecified time of day, without clinical context and without a standardized protocol, tells you almost nothing meaningful about whether your adrenal glands are functioning properly.

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What Real Adrenal Insufficiency Actually Looks Like

None of this means that disorders of cortisol don’t exist. They absolutely do and they are serious.

True adrenal insufficiency, known as Addison’s disease when it involves the adrenal glands themselves, is a real endocrine condition in which the adrenal cortex cannot produce sufficient cortisol and often aldosterone as well. It is not common, prevalence is estimated at roughly 100 to 140 cases per million people in developed countries but it is potentially life-threatening and absolutely deserves prompt diagnosis and treatment.

The clinical picture of true adrenal insufficiency is specific. It includes:

Fatigue and profound weakness — but not the kind that fluctuates with how busy your week is. This is severe, progressive, disabling fatigue that worsens over time and does not respond to rest.

Unintentional weight loss — often significant, not explained by changes in diet or activity.

Gastrointestinal symptoms — nausea, vomiting, abdominal pain, and sometimes diarrhea. These can be severe.

Hypotension — low blood pressure, often with pronounced dizziness or lightheadedness on standing.

Salt craving — a specific, intense craving for salty foods, related to aldosterone deficiency and the resulting sodium loss.

Hyperpigmentation — darkening of the skin, particularly in skin creases, scars, and areas of friction. This is caused by elevated ACTH driving melanocyte stimulating hormone, and it is a distinctive finding not present in most other causes of fatigue.

Laboratory abnormalities — hyponatremia, hyperkalemia, hypoglycemia, and anemia are common findings.

This is a recognizable, specific clinical picture. It is not vague. It does not describe the experience of feeling tired and overwhelmed by modern life. When these features are present and particularly the combination of profound weakness, weight loss, GI symptoms, hypotension, salt craving, and hyperpigmentation then adrenal insufficiency belongs in the differential and warrants prompt evaluation.

How is it actually diagnosed? The gold standard is the ACTH stimulation test, performed in a clinical setting. A synthetic form of ACTH is administered, and cortisol levels are measured at 30 and 60 minutes. This test is assay-dependent and requires interpretation by a physician who knows your full clinical picture.

A home spit kit does not accomplish this. It cannot.

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The Nuance That Matters

Chronic stress is real. And it does affect the HPA axis in ways that are clinically meaningful.

Prolonged psychological and physiological stress can dysregulate cortisol rhythms disrupting the normal morning peak, altering the Cortisol Awakening Response, and affecting how the HPA axis responds to acute stressors. There is even emerging evidence that in cases of extreme, sustained chronic stress, cortisol reactivity may be reduced over time through a process of HPA inhibition. This is an active area of research.

But, and this is the critical distinction, HPA axis dysregulation is not the same as adrenal gland failure. The mechanism is different, the clinical significance is different, and most importantly, the appropriate response is different.

When chronic stress is disrupting your physiology, the evidence-based interventions are: addressing sleep disorders, treating depression or anxiety if present, consistent physical activity, cognitive behavioral therapy (which has Level I evidence for fatigue-related conditions), and reducing or meaningfully addressing the sources of stress. None of these interventions require a cortisol test. None of them are served by an “adrenal support” supplement protocol.

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Why This Matters Beyond Getting the Science Right

The reason I am writing about this is not to be dismissive of people who are genuinely suffering. If you have been told you have adrenal fatigue and that explanation felt validating, I understand why. Fatigue is real. Being exhausted all the time and not having answers is genuinely distressing. When someone offers you an explanation and a protocol, that can feel like relief.

But here is what concerns me.

First, the “adrenal fatigue” narrative can delay real diagnosis. If someone with iron deficiency, sleep apnea, hypothyroidism, or early autoimmune disease is told their problem is their adrenals, and spends months on a supplement protocol, the actual cause goes unidentified and untreated.

Second, and more seriously: some practitioners prescribe cortisol analogs or compounded cortisol preparations to patients diagnosed with adrenal fatigue. When cortisol is taken exogenously by someone with normally functioning adrenal glands, the adrenal glands receive feedback to suppress their own production. When that exogenous cortisol is stopped abruptly the adrenal glands may remain suppressed for months, creating a real risk of adrenal insufficiency and in severe cases, adrenal crisis. A treatment for a condition that doesn’t exist can cause the condition it claims to treat.

That is not a theoretical risk. It is a documented clinical consequence. It is why the Endocrine Society and academic endocrinologists have been increasingly vocal about this issue.

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What to Do If You’re Exhausted and Looking for Answers

If fatigue is affecting your quality of life, you deserve a thorough evaluation, the kind we walked through in Week 1 of this series. That means a comprehensive history, a physical examination, and targeted laboratory testing guided by your clinical picture.

If you are specifically worried about your cortisol or your adrenal function, bring that concern to your physician. A proper evaluation would include morning cortisol, ACTH level, and if indicated, a cosyntropin stimulation test and can definitively assess adrenal function. These are validated, guideline-supported tests interpreted by a clinician who knows you.

That is what the evidence supports. Not a kit. Not a quiz. Not a supplement protocol built around a diagnosis that no endocrinology society in the world recognizes.

You deserve better than that.

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Next week we’re tackling sleep, not just how many hours you’re getting, but what’s happening during those hours, and why for many women the problem isn’t the amount of sleep but the quality of what the body is doing while you’re in bed.

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Sources:

• Cadegiani FA, Kater CE. Adrenal fatigue does not exist: a systematic review. BMC Endocrine Disorders. 2016;16(1):48. doi:10.1186/s12902-016-0128-4
• Hamrahian AH, et al. Pseudo-endocrine Disorders: Recognition, Management, and Action. Journal of the Endocrine Society. 2024;9(1):bvae226. doi:10.1210/jendso/bvae226
• Bornstein SR, et al. Diagnosis and Treatment of Primary Adrenal Insufficiency: An Endocrine Society Clinical Practice Guideline. Journal of Clinical Endocrinology & Metabolism. 2016;101(2):364–389. doi:10.1210/jc.2015-1710
• Endocrine Society. Adrenal Fatigue. endocrine.org

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This content is for educational purposes and is not a substitute for individualized medical care. If you are experiencing symptoms that concern you, please discuss them with your healthcare provider.