Adrenal Fatigue vs. HPA Axis Dysfunction: What's Real, What Isn't, and What Helps

You've been running hard for years. Now you drag yourself out of bed, need coffee to function by 10, crash at 3, and get a second wind at 10 PM that keeps you scrolling until midnight. Salt and sugar cravings, a short fuse, and colds that won't quit.

Someone online says it's adrenal fatigue. Your doctor says adrenal fatigue doesn't exist.

They're both partly right.

What "adrenal fatigue" claims

The adrenal fatigue idea, popularized in the late 1990s, says that chronic stress overworks the adrenal glands until they can't make enough cortisol. The glands become "fatigued," and you feel exhausted.

The problem is that the evidence doesn't support the glands themselves wearing out.

In 2016, a systematic review in BMC Endocrine Disorders looked at 58 studies and found no proof that "adrenal fatigue" is a real medical condition. The studies were inconsistent, many used unreliable cortisol tests, and none showed the adrenal glands losing their ability to produce cortisol from stress alone.

Most endocrinologists agree. And there's a reason doctors are cautious: a real condition, adrenal insufficiency (Addison's disease), does involve adrenals that can't make enough cortisol. It's rare, it can be life-threatening, and it needs proper testing and medication, not supplements. Symptoms include severe fatigue, weight loss, dizziness on standing, salt craving, and darkening of the skin.

What is real: the HPA axis

Cortisol isn't controlled by the adrenals alone. It's controlled by a chain called the HPA axis:

• Hypothalamus in the brain senses stress and sends a signal
• Pituitary gland passes it on with ACTH
• Adrenal glands release cortisol in response

The adrenals are usually fine. What changes with chronic stress is the signaling and the rhythm. That's the useful idea that "adrenal fatigue" got wrong in name.

Cortisol's daily rhythm

Healthy cortisol follows a curve. It jumps in the first 30 to 45 minutes after waking (the cortisol awakening response), then falls steadily through the day to its lowest point around bedtime. That rise gets you up. The fall lets you sleep.

With long-term stress, poor sleep, shift work, or illness, the curve can flatten or shift. Morning cortisol may be low, so you wake unrefreshed. Evening cortisol may stay high, so you're wired at night.

This isn't just a theory. A 2017 meta-analysis of 80 studies in Psychoneuroendocrinology found that a flatter daily cortisol slope was linked to worse outcomes in 10 of 12 health areas studied, with the strongest links to inflammation and immune problems, and links to fatigue, depression, and obesity.

So your stress system can be out of rhythm in a measurable way. That's HPA axis dysfunction. For the two most common patterns, see The Bossy Betty Archetype (the crash) and The Wired Wendy Archetype (the flipped rhythm).

How cortisol is tested

A single morning blood cortisol shows one moment. It's the right first test to rule out adrenal insufficiency, but it can't show your rhythm.

To see the curve, cortisol is measured several times across a day:

• Salivary cortisol, usually four samples: on waking, late morning, afternoon, and bedtime. Some panels add samples right after waking to capture the awakening response.
• Dried urine testing, which also shows how cortisol is being broken down.

These tests are best used to see a pattern alongside your symptoms, not to diagnose a disease. Results shift with a bad night's sleep, a hard workout, or an argument the day before. And if testing suggests very high or very low cortisol, the next step is proper medical testing for Cushing's syndrome or adrenal insufficiency.

Be careful with "adrenal support" supplements

This is the part that worries endocrinologists most, and for good reason.

A 2018 study in Mayo Clinic Proceedings tested 12 supplements sold for adrenal fatigue. All 12 contained thyroid hormone, and 7 contained steroid hormones, none of which were listed on the label. Taking hidden thyroid or steroid hormones can cause palpitations, bone loss, and anxiety. Stopping steroids suddenly after taking them for a while can be dangerous.

"Adrenal glandulars," made from animal adrenal tissue, are the biggest concern. If you're taking one, talk to your clinician before you stop or change it.

What helps

The goal isn't to "rest" your adrenals. It's to restore the rhythm.

Anchor the morning

• Get outside light within an hour of waking. Morning light is one of the strongest signals for the cortisol rise.
• Eat breakfast with protein within a couple of hours of waking.
• Wait a little before coffee if you're relying on it to function, and keep it before noon.

Protect the evening

• Dim lights and screens in the last hour before bed.
• Keep hard workouts earlier in the day if you're wired at night.
• Keep a consistent bedtime and wake time, including on weekends.

Steady your blood sugar

Blood sugar crashes trigger cortisol. Regular meals with protein, fiber, and fat reduce the 3 PM crash. See Why You Crash at 3 PM.

Train your nervous system

Slow breathing, walks outdoors, time with people you trust, and real recovery days all lower stress-system activity. See Nervous System Regulation and Hormones.

Ashwagandha, with a caution

Ashwagandha is the best-studied herb for stress. In a 2019 eight-week randomized trial, 600 mg a day of ashwagandha root extract lowered serum cortisol and anxiety scores compared with placebo. The trial was small, and results across studies vary.

There's a safety caution. In July 2026, Australia's medicines regulator issued its second alert about rare cases of liver injury linked to ashwagandha. Avoid it if you have or have had liver problems, and stop and see a doctor if you notice yellowing skin or eyes, dark urine, nausea, or unusual tiredness. It's also not recommended in pregnancy or with an overactive thyroid. Ashwagandha is available through my Fullscript dispensary.

Check what else could be draining you

Many things look like a stress-system problem. Before blaming cortisol, it's worth checking:

• Thyroid, including antibodies. See Hashimoto's With a Normal TSH.
• Iron and ferritin, B12, and vitamin D
• Sleep apnea, which is underdiagnosed in women
• Blood sugar and insulin resistance
• Perimenopause, which disrupts sleep and stress tolerance
• Depression and anxiety

What you can do now

1. Rule out the serious stuff. If you have weight loss, dizziness on standing, or darkening skin, ask for a morning cortisol test.
2. Map your rhythm. Note when you feel flat and when you feel wired. A four-point cortisol test can confirm the pattern.
3. Check your supplements for adrenal glandulars or hidden hormones.
4. Anchor your mornings and protect your evenings for four weeks before judging what's working.

Your adrenals almost certainly aren't "burnt out." But your stress system can lose its rhythm, and that rhythm can be rebuilt.

References

1. Cadegiani FA, Kater CE. Adrenal fatigue does not exist: a systematic review. BMC Endocr Disord. 2016;16:48. View source
2. Adam EK, Quinn ME, Tavernier R, et al. Diurnal cortisol slopes and mental and physical health outcomes: a systematic review and meta-analysis. Psychoneuroendocrinology. 2017. Summary from Northwestern University. View source
3. Akturk HK, et al. Over-the-counter "adrenal support" supplements contain thyroid and steroid-based adrenal hormones. Mayo Clin Proc. 2018. Summary in Free Malaysia Today (Reuters). View source
4. Salve J, Pate S, Debnath K, Langade D. Adaptogenic and anxiolytic effects of ashwagandha root extract in healthy adults: a double-blind, randomized, placebo-controlled clinical study. Cureus. 2019;11(12):e6466. View source
5. TGA makes second safety alert on ashwagandha and liver injury. The Medical Republic. July 2026. View source