Short answer: Non-classic congenital adrenal hyperplasia (NCAH) is a mild, inherited condition in which the adrenal glands make too many androgens because the enzyme 21-hydroxylase works only partly. The Endocrine Society’s 2018 hirsutism guideline says it is found in 4.2% of women with androgen excess worldwide, and it looks very similar to PMOS (formerly PCOS). It is picked up with an early-morning 17-hydroxyprogesterone blood test: a value above about 170-200 ng/dL (5-6 nmol/L) calls for more testing, and 1,000 ng/dL (30 nmol/L) or more confirms it. Hair growth is usually treated the same way as in PMOS, with the pill and anti-androgens, while steroid tablets are used mainly for fertility.
NCAH is one of the few causes of hirsutism with a specific blood test, a genetic basis and implications for future pregnancies. This guide explains who should be tested, what the numbers mean and how treatment differs.
What is non-classic congenital adrenal hyperplasia?
NCAH is the mild form of congenital adrenal hyperplasia, a group of inherited conditions affecting the adrenal glands, which sit on top of the kidneys. It is most often caused by a partial lack of the enzyme 21-hydroxylase, which the adrenal glands need to make cortisol.[1], [2]
When the enzyme works poorly, a hormone called 17-hydroxyprogesterone (17-OHP) is not converted efficiently. The body’s stress-hormone signal, ACTH, keeps pushing the adrenal glands, and more of the building blocks are turned into androgens.[2] In the non-classic form, the enzyme still works at about 10% to 70% of normal.[2] That is why NCAH is far milder than classic CAH, which is usually found in newborns and affects about 1 in 14,000 to 1 in 18,000 births.[3]
How common is NCAH, and who is most at risk?
NCAH is one of the most common inherited hormone conditions, but how common depends on ancestry and on which study you read. The 2018 Endocrine Society CAH guideline cites older estimates of 1 in 500 to 1 in 1,000 in the general white population, and a more recent genetic analysis that put it at about 1 in 200 in the US.[3]
| Population | Estimate | Source |
|---|---|---|
| General white population | 1 in 500 to 1 in 1,000 (older estimate); about 1 in 200 (newer genetic estimate) | Endocrine Society CAH guideline, 2018[3] |
| Ashkenazi Jewish (1985 estimate) | 3.7% | Speiser et al., 1985[5] |
| Ashkenazi Jewish (2017 genetic testing, 200 people) | About 0.5% affected; 15% carriers | Hannah-Shmouni et al., 2017[6] |
| US white, no specific ethnicity (2017, 200 people) | About 0.5% (1 in 200); 9.5% carriers | Hannah-Shmouni et al., 2017[6] |
| Hispanic (1985 estimate) | 1.9% | Speiser et al., 1985[5] |
| Former Yugoslavia (1985 estimate) | 1.6% | Speiser et al., 1985[5] |
| Italian (1985 estimate) | 0.3% | Speiser et al., 1985[5] |
The 1985 figures, which are still widely quoted, came from indirect genetic methods. When researchers tested 200 Ashkenazi Jewish and 200 white Americans with modern gene testing in 2017, they found the Ashkenazi rate was lower than previously reported and concluded that NCAH is common regardless of ethnicity.[6]
Among women who already have signs of androgen excess, the Endocrine Society reports NCAH in 4.2% worldwide, 1% to 2% among US white and Hispanic women, 3% to 6% in Spain, France, Italy and Canada, and 5% to 10% in the Middle East. It is relatively unusual among African American women.[1] Clinic studies found it in 4.3% of 950 women in Italy and 1.6% of 873 women in the US.[7], [8]
What are the symptoms of NCAH in women?
Hirsutism is the most common symptom, reported in 71% to 96% of women with NCAH in studies summarized in a 2019 review.[2] Other common signs are:
- Irregular or missing periods[2]
- Acne, in about a third of women[2]
- Difficulty getting pregnant, estimated at about 11%[2]
- In children, early pubic or underarm hair (premature pubarche)[2], [3]
Some people with NCAH have no symptoms and normal fertility.[2] Unlike classic CAH, NCAH is not usually life-threatening, but about a third of people with NCAH have a lower-than-normal cortisol response on testing.[2]
Why do doctors often miss NCAH?
Doctors miss NCAH mainly because it looks almost exactly like PMOS, the condition called polycystic ovary syndrome (PCOS) until its renaming in 2026.[4] A 2019 review calls NCAH “the big mimicker of PCOS.”[2] Both cause hirsutism, acne and irregular periods. Other reasons it slips through:
- The test needs the right timing. A randomly timed 17-OHP test can be normal in NCAH, and 17-OHP is naturally higher after ovulation in about half of healthy women, which can mislead in the other direction.[3], [2]
- Screening is not universal. The Endocrine Society suggests screening women who have raised androgen levels, so a woman with hirsutism but borderline blood tests may never get the test.[1]
- PMOS is diagnosed by exclusion. The 2023 International PCOS guideline lists congenital adrenal hyperplasia among the causes to consider when androgen levels are well above the reference range, so women with milder results may not be checked for it.[9]
If you have hirsutism and Ashkenazi Jewish, Hispanic, Mediterranean or Middle Eastern ancestry, or a family member with CAH, it is reasonable to ask whether you have been screened.[1], [5]
How is NCAH tested? 17-hydroxyprogesterone levels explained
NCAH is tested with a blood test for 17-hydroxyprogesterone taken early in the morning, ideally in the follicular phase (the first part of your cycle, after your period starts). The Endocrine Society CAH guideline recommends taking the sample before 8 AM and, if possible, measuring it with a precise method called liquid chromatography-tandem mass spectrometry (LC-MS/MS).[3] If you have no periods, the hirsutism guideline says the test can be done on any day.[1]
| Result | What it usually means | Source |
|---|---|---|
| Early-morning 17-OHP below about 170-200 ng/dL (5.15-6.0 nmol/L) | NCAH unlikely | Endocrine Society hirsutism guideline, 2018[1] |
| Early-morning 17-OHP above about 170-200 ng/dL (above 2 ng/mL, or 6 nmol/L) | Needs further testing with an ACTH stimulation test | Endocrine Society, 2018; Livadas and Bothou, 2019[1], [2] |
| 17-OHP of 1,000-1,500 ng/dL (30-45 nmol/L) or more, either before or after ACTH stimulation | Confirms NCAH | Endocrine Society hirsutism guideline, 2018[1] |
| Borderline or unclear results | Genetic testing of the CYP21A2 gene | Endocrine Society CAH guideline, 2018[3] |
According to the Endocrine Society, the screening cutoff of 170-200 ng/dL is about 95% sensitive and 90% specific for NCAH, which means it catches most cases but also flags some women who do not have it.[1] Units differ between countries: 100 ng/dL equals 1 ng/mL, or about 3 nmol/L, as the guideline’s paired figures show.[1] Lab methods and reference ranges also vary, so always use the range printed on your own report.
The ACTH stimulation test (also called a cosyntropin or Synacthen test) means you get an injection of synthetic ACTH, and your blood is tested before and after the injection. The guideline recommends measuring the full set of adrenal hormones after stimulation when results are borderline.[3] Read more about the other tests in our guide to blood tests and labs for hirsutism.
Is NCAH genetic? What it means for family planning
Yes. NCAH is inherited in an autosomal recessive way, which means you need a changed CYP21A2 gene from both parents to have it. People who carry one changed copy are called carriers and usually have no symptoms.[2] A 2019 review estimates that 1 in 10 to 1 in 25 people are carriers, depending on the population.[2]
Many women with NCAH carry one “severe” gene change, the kind that causes classic CAH. If their partner also carries a severe change, a baby could be born with classic CAH.[10] In an international study of 203 pregnancies in 101 women with NCAH, 2.5% of the 162 babies born alive had classic CAH and at least 14.8% had NCAH.[10]
A 2019 review estimates the chance of a child with classic CAH at about 1 in 120 if the father’s genes are unknown, zero if he carries no relevant gene change, and 1 in 4 if he carries one.[2] That is why the Endocrine Society CAH guideline recommends genetic counseling by professionals familiar with CAH for adults and their partners who are planning a pregnancy, and the review suggests offering gene testing to partners.[3], [2] Read more in is hirsutism hereditary.
How is NCAH treated?
Treatment depends on your goal. For unwanted hair, the Endocrine Society says the approach is the same as for PMOS. For fertility, steroid tablets are often used. People without symptoms usually need no treatment at all.[1], [3]
Birth control pill and anti-androgens for hirsutism
Evidence: Strong The Endocrine Society suggests starting with an oral contraceptive and adding an anti-androgen, such as spironolactone, after 6 months if needed.[1] It notes that although glucocorticoids may improve hirsutism, the pill and anti-androgens may be more effective.[1] Anti-androgens can harm a developing baby, so they should only be used with reliable contraception, and women planning pregnancy should talk to their doctor about these risks.[1] Our hirsutism medication guide covers the options in detail.
Steroid tablets (glucocorticoids)
Evidence: Moderate Glucocorticoids such as prednisone or dexamethasone lower ACTH and so reduce adrenal androgen production.[2] The Endocrine Society hirsutism guideline only suggests them for hair when the pill or anti-androgens have not worked well enough or are not tolerated.[1] The CAH guideline suggests glucocorticoids for adult women with NCAH who have bothersome androgen excess or infertility, but rates the evidence as low quality.[3] Long-term use can cause side effects of excess cortisol, including bone loss.[2] Your doctor will decide on the dose; the guidelines list low doses, but these are not personal advice.[1]
Fertility and pregnancy
Evidence: Moderate For women with NCAH who want to get pregnant, the Endocrine Society hirsutism guideline suggests glucocorticoids to help ovulation.[1] For women with infertility or a previous miscarriage, the CAH guideline recommends a glucocorticoid that does not cross the placenta.[3] In the international study of 203 pregnancies, miscarriage occurred in 25.4% of pregnancies before the mother’s NCAH was diagnosed and in 6.2% after diagnosis.[10] This was an observational study, so other factors may have played a part.
Hair removal
Evidence: Strong Laser, electrolysis and other hair removal methods work the same way in NCAH as in other hirsutism. The Endocrine Society suggests combining hair removal with medication in women with raised androgens to limit regrowth.[1]
Do you need stress-dose steroids?
Usually not. The CAH guideline suggests extra steroid cover during illness or surgery only for people with NCAH who have a low cortisol response on the ACTH test, or those whose own adrenal function is suppressed by steroid treatment.[3], [2]
What should you ask your doctor about NCAH?
- Has my 17-hydroxyprogesterone been tested, and was it taken early in the morning in the first part of my cycle?
- Is my result clearly normal, or borderline enough to need an ACTH stimulation test?
- Should I have genetic testing, and should my partner be tested before we try for a baby?
- Do I need treatment at all, and if so, is the pill or a steroid the better option for my goals?
- Is my cortisol response normal, or do I need a steroid emergency plan?
An endocrinologist (hormone specialist) can run and interpret these tests. Our which doctor should you see for hirsutism tool can help you decide where to start.
When should you see a doctor?
See a doctor if unwanted hair bothers you, especially with irregular periods, acne or trouble getting pregnant.[11] Get an urgent appointment if thick, dark hair starts growing suddenly, or your voice becomes deeper.[11] Other red flags are rapidly worsening hair growth, an enlarged clitoris and periods that stop. These are not typical of NCAH and can point to a rare androgen-producing tumor.[1]
Frequently asked questions
Can NCAH be mistaken for PCOS (PMOS)?
Yes, very often. Both cause hirsutism, acne and irregular periods, and NCAH has been called “the big mimicker of PCOS.”[2] A morning 17-hydroxyprogesterone test is the main way to tell them apart. Our article on idiopathic hirsutism includes a table comparing PMOS, NCAH and hirsutism with normal hormones.
What 17-hydroxyprogesterone level indicates NCAH?
According to the Endocrine Society, an early-morning level above about 170-200 ng/dL (5-6 nmol/L) suggests NCAH and needs follow-up, and a level of 1,000-1,500 ng/dL (30-45 nmol/L) or more, before or after ACTH stimulation, confirms it.[1] Labs differ, so use your own lab’s range.
Can you get pregnant with NCAH?
Yes, many women with NCAH have children. Fertility problems affect an estimated 11%, and glucocorticoids can help ovulation.[2], [1] Genetic counseling before pregnancy is recommended because of the small risk of a baby with classic CAH.[3], [10]
Do I need steroids for life if I have NCAH?
No. The CAH guideline recommends against steroid treatment in people with NCAH who have no symptoms, and suggests offering to stop it once symptoms resolve.[3] For hair, the pill and anti-androgens are usually tried first.[1]
Key takeaways
- NCAH is an inherited partial 21-hydroxylase deficiency that makes the adrenal glands produce extra androgens.
- It is found in about 4% of women with androgen excess worldwide and closely mimics PMOS.
- The screening test is an early-morning, early-cycle 17-hydroxyprogesterone; above about 170-200 ng/dL needs follow-up, and 1,000 ng/dL or more confirms it.
- Hair is treated like PMOS hirsutism, with the pill and anti-androgens; steroid tablets are used mainly for fertility.
- Women with NCAH have about a 2.5% chance of a baby with classic CAH, so genetic counseling and partner testing are recommended before pregnancy.
Sources
- Martin KA, Anderson RR, Chang RJ, et al. Evaluation and Treatment of Hirsutism in Premenopausal Women: An Endocrine Society Clinical Practice Guideline. J Clin Endocrinol Metab. 2018;103(4):1233-1257. PubMed 29522147
- Livadas S, Bothou C. Management of the Female With Non-classical Congenital Adrenal Hyperplasia (NCCAH): A Patient-Oriented Approach. Front Endocrinol. 2019;10:366. Link
- Speiser PW, Arlt W, Auchus RJ, et al. Congenital Adrenal Hyperplasia Due to Steroid 21-Hydroxylase Deficiency: An Endocrine Society Clinical Practice Guideline. J Clin Endocrinol Metab. 2018;103(11):4043-4088. PubMed 30272171
- Teede HJ, Bahri Khomami M, Morman R, et al. Polyendocrine metabolic ovarian syndrome, the new name for polycystic ovary syndrome: a multistep global consensus process. Lancet. 2026;407(10545):2329-2339. PubMed 42119588
- Speiser PW, Dupont B, Rubinstein P, Piazza A, Kastelan A, New MI. High frequency of nonclassical steroid 21-hydroxylase deficiency. Am J Hum Genet. 1985;37(4):650-667. PubMed 9556656
- Hannah-Shmouni F, Morissette R, Sinaii N, et al. Revisiting the prevalence of nonclassic congenital adrenal hyperplasia in US Ashkenazi Jews and Caucasians. Genet Med. 2017;19:1276-1279. PubMed 28541281
- Carmina E, Rosato F, Jannì A, Rizzo M, Longo RA. Extensive clinical experience: relative prevalence of different androgen excess disorders in 950 women referred because of clinical hyperandrogenism. J Clin Endocrinol Metab. 2006;91(1):2-6. PubMed 16263820
- Azziz R, Sanchez LA, Knochenhauer ES, et al. Androgen excess in women: experience with over 1000 consecutive patients. J Clin Endocrinol Metab. 2004;89(2):453-462. Link
- Teede HJ, Tay CT, Laven JJE, et al. Recommendations From the 2023 International Evidence-based Guideline for the Assessment and Management of Polycystic Ovary Syndrome. J Clin Endocrinol Metab. 2023;108(10):2447-2469. PubMed 37580314
- Moran C, Azziz R, Weintrob N, et al. Reproductive outcome of women with 21-hydroxylase-deficient nonclassic adrenal hyperplasia. J Clin Endocrinol Metab. 2006;91(9):3451-3456. PubMed 16822826
- NHS. Excessive hair growth (hirsutism). Accessed October 2026. Link
This article is for education and is not medical advice. Talk to a doctor about diagnosis and treatment.