Does high cortisol cause hair loss? What the evidence shows

Does high cortisol cause hair loss? Reviews propose that long-lasting stress, and the cortisol it raises, can disrupt the hair growth cycle. But a proposed mechanism is not proof that your cortisol level is the reason your hair is thinning. Hair loss has many more common causes, and the clinical sources on Cushing’s syndrome and low cortisol don’t list hair loss among their symptoms.

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What causes hair loss

MedlinePlus says losing up to 100 scalp hairs a day is normal, and that in most people they grow back. Many men and some women lose hair as they get older. It lists other causes:

• diseases such as thyroid problems, diabetes or lupus
• certain medicines, and chemotherapy for cancer
• stress
• a low-protein diet or poor nutrition
• family history

It adds that treatment depends on the cause, and that in some cases treating the underlying cause corrects the problem.

Two of these can be checked with a blood test. NIDDK lists dry, thinning hair among the many symptoms of an underactive thyroid. MedlinePlus says a TSH test shows how well the thyroid is working. And ferritin is a marker of the body’s iron stores. In a 2025 study of 100 women, 50 with a type of shedding called telogen effluvium, average ferritin was lower in the women with shedding (24.3 versus 44.8 ng/mL). It was a single-point comparison, so it shows an association and can’t show which came first (Cureus, 2025).

What the cortisol idea rests on

A 2025 narrative review of mental health and hair loss describes how an overactive stress system, with raised cortisol, could disrupt the normal hair cycle. For alopecia areata, an autoimmune type of hair loss, it describes the proposal that prolonged cortisol exposure interferes with immune signalling around the follicle. The same review says psychological stress can trigger or worsen several kinds of hair loss (Cureus, 2025).

Two things to keep in mind. First, a narrative review collects findings and proposes explanations. It describes mechanisms. It doesn’t test whether people with higher cortisol lose more hair. Second, stress and cortisol aren’t the same thing. The review ties hair loss to chronic psychological stress, and as the cortisol and stress page explains, studies of long-term stress and cortisol disagree.

So “linked” is the strongest word the sources support, and for a given person, the cause of the hair loss is a question for a clinician.

What about low cortisol?

People also ask whether low cortisol can cause hair loss. The NIDDK pages on adrenal insufficiency and on Cushing’s syndrome list their symptoms, and hair loss is not among them. For Cushing’s syndrome, NIDDK lists extra hair on the face, neck, chest, abdomen and thighs in women, which is the opposite problem. No source used for this page links low cortisol to hair loss.

Cortisol measured in hair is a different thing

Hair can also be used to measure cortisol. A 2021 review calls hair cortisol a promising marker of longer-term HPA axis activity (Life, 2021). That is a research and testing method. It tells you nothing on its own about whether cortisol is why you are losing hair. See saliva, urine and hair tests.

Is cortisol-related hair loss reversible?

The sources don’t answer that, because none of them shows cortisol as the cause. What MedlinePlus says is general: treatment depends on the cause, and treating an underlying cause corrects the problem in some cases. That is why finding the cause comes first.

Biotin and hormone tests

High-dose biotin supplements are often taken for hair and nails. A 2024 paper in the Journal of the Endocrine Society says high-dose biotin can make some hormone results falsely high or falsely low, depending on the lab method. It names cortisol and TSH among the tests that can be affected. Tell the clinician and the lab if you take biotin, and ask them what to do before a test (J Endocr Soc, 2024).

When to see a clinician

A clinician can look for the cause of hair loss. It is worth booking one when you can’t explain the hair loss, or when it comes with other symptoms. Examples include:

• fatigue, weight gain, feeling cold and dry skin, which are on the list for an underactive thyroid
• easy bruising, wide purple stretch marks, a rounded face and weak muscles, which are on the list for Cushing’s syndrome (high cortisol)
• long-lasting fatigue, weight loss and loss of appetite, which are on the list for too little cortisol (low cortisol)

If a medicine could be involved, ask the prescriber. Don’t stop it on your own, and never stop a steroid medicine without the prescriber’s advice.

If you want a number to take with you, a ferritin test checks iron stores and a TSH test checks the thyroid. Neither is a hair loss test, and a result is something to go over with a clinician.

• TSHA common first check of the thyroid $39 See this test at HealthLabs

Sold by HealthLabs. Prices checked November 2026. Not available in ND, RI, NY, NJ, MD and HI. We earn a commission on sales.