Health condition
Non-classic CAH
Non-classic congenital adrenal hyperplasia is a mild, late-presenting form of 21-hydroxylase deficiency that mimics polycystic ovary syndrome, with acne, excess hair and irregular periods - a morning 17-hydroxyprogesterone blood test screens for it.
Why trust this guide
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Editorial team
Written by our editorial team from the UK sources listed on each page.
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Sourced from guidance
Checked against current NHS and UK specialist society guidance at the time of review.
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Current for 2026
Reviewed on 2026-09-27 with the next review scheduled for 2027-09-27.
Key facts
The essentials at a glance.
The symptoms to recognise, when to seek help, which specialist to see, and what treatment usually involves.
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Presents in adolescence or adulthood with hirsutism, acne, irregular periods or subfertility - often labelled PCOS
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Screening test: early-morning follicular-phase 17-hydroxyprogesterone; a synacthen-stimulated level confirms it
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Cortisol production is usually adequate, so adrenal crisis is rare
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Treatment is symptom-led: many women need only the approaches used for PCOS, with low-dose glucocorticoids reserved for selected cases including some fertility treatment
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Genetic counselling matters when planning a family, as a partner carrying a severe mutation changes the risks
Understanding the condition
What it is and what happens next.
What causes it, how it is diagnosed, and the treatment routes available in the UK.
What it is and how it feels
Non-classic CAH is one of the commonest inherited endocrine conditions, yet routinely missed because it wears PCOS clothing: oily skin, acne, unwanted hair growth, scalp thinning and erratic cycles beginning around puberty or later. The enzyme deficiency is partial, so cortisol is broadly maintained and salt-wasting crises do not occur, but androgen precursors run high enough to disturb skin, hair and ovulation.
Diagnosis and treatment routes
The screen is a morning 17-hydroxyprogesterone taken in the first half of the cycle; borderline results are clarified with a short synacthen test, and genotyping confirms it. Treatment is pragmatic - combined pill, anti-androgens or cosmetic approaches for most, with glucocorticoids mainly for subfertility - plus genetic advice before pregnancy. If your PCOS diagnosis has never included this test, asking for it is reasonable. NHS gynaecology-endocrine waits are long; a private endocrinologist can typically see you within about two weeks.
Seeing a specialist
Who to see, and how quickly you can be seen.
The specialist for this condition is usually a consultant endocrinologist or reproductive endocrinologist. Your GP can refer you on the NHS, or you can arrange a private consultation directly.
A quiet reminder
This guide is for information, not medical advice.
Your GP knows your history and can tell you which parts apply to you. If in doubt, see them - and seek urgent care for any of the emergency symptoms described above.
Frequently asked
Common questions about Non-classic CAH.
Quick, plain-English answers to what people ask us most.
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What is non-classic congenital adrenal hyperplasia (CAH)?
Non-classic CAH is a milder, later-onset form of an inherited condition affecting adrenal hormone production, typically presenting with symptoms of excess androgen hormones rather than the more severe features seen in classic CAH diagnosed in infancy.
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What causes non-classic CAH?
It's caused by partial deficiency of an enzyme, most commonly 21-hydroxylase, involved in adrenal hormone production, inherited in an autosomal recessive pattern, with milder gene mutations than those causing classic CAH.
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What are the symptoms of non-classic CAH?
Symptoms can include early puberty signs, excess hair growth, acne, irregular periods, and fertility difficulties in women, often not appearing until childhood, adolescence or even adulthood.
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Is non-classic CAH hereditary?
Yes, it's inherited in an autosomal recessive pattern, meaning both parents carry one copy of a relevant gene mutation without necessarily having symptoms themselves.
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Can non-classic CAH be treated?
Yes, treatment with corticosteroid replacement can help normalise hormone levels and improve symptoms such as excess hair growth or menstrual irregularities, though not everyone with non-classic CAH needs treatment if symptoms are mild.
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How is non-classic CAH diagnosed?
Diagnosis involves blood tests measuring specific adrenal hormone precursors, sometimes with a stimulation test, and genetic testing to confirm the diagnosis and inform family counselling.
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When should I see an endocrinologist about suspected non-classic CAH, and how quickly can I be seen privately?
See an endocrinologist for unexplained excess hair growth, irregular periods or early puberty signs. A private endocrinologist can typically arrange assessment within about two weeks.