Short answer: Idiopathic hirsutism is male-pattern hair growth in a woman whose androgen (male hormone) levels and ovulation are normal and who has no other hormonal condition. The Endocrine Society’s 2018 guideline estimates it accounts for 5% to 20% of women with hirsutism. The leading explanation is hair follicles that react more strongly to normal amounts of androgens. It is treated with the same options as other hirsutism, mainly hair removal, the birth control pill and anti-androgen medicines.
“Idiopathic” is a medical word for “no cause found.” If your blood tests came back normal, your periods are regular and you were told you “just have hirsutism,” this is probably the label your doctor had in mind. It can feel unsatisfying, because the hair is real even when the hormone results look normal. This article explains what the diagnosis means, why it happens, how doctors reach it and what helps.
What is idiopathic hirsutism?
Idiopathic hirsutism is hirsutism (coarse, dark hair in a male pattern, such as the chin, upper lip, chest or lower belly) without high androgen levels and without signs of a hormonal disorder. That is how the Endocrine Society’s 2018 guideline defines it, and the guideline uses the term for women with regular periods who have no other clinical signs of PMOS (formerly PCOS).[1]
Definitions differ a little between expert groups, which is worth knowing if you read different sources:
- Endocrine Society (2018): Normal androgen levels and regular periods. The guideline notes that some of these women have polycystic-looking ovaries on ultrasound and could technically meet one criterion for “ovulatory PCOS.”[1]
- Androgen Excess and PCOS Society (2012): Normal androgen levels, normal ovulation and normal ovaries on ultrasound. This is the stricter definition.[2]
- Older usage: Some earlier papers used the term for any hirsutism of unknown cause, whatever the androgen levels.[3]
A related but separate label is idiopathic hyperandrogenism: Raised androgen levels with regular ovulation and no other cause. The Androgen Excess and PCOS Society notes that only accurate testosterone tests can tell the two apart.[2] In 2023, a group of researchers who study the condition suggested renaming idiopathic hirsutism “normoandrogenic hirsutism,” meaning hirsutism with normal androgens.[3]
How common is idiopathic hirsutism?
Idiopathic hirsutism is the cause in about 5% to 20% of women with hirsutism, according to the Endocrine Society, and in about 5% to 10% of women in large specialist-clinic studies.[1], [4], [5], [2] PMOS is far more common. The table shows the main clinic studies.
| Study | Who was studied | Share with idiopathic hirsutism |
|---|---|---|
| Endocrine Society guideline, 2018[1] | Summary of published studies | 5% to 20% of hirsute women |
| Carmina et al., 2006, Italy[4] | 950 women referred for androgen excess | 7.6% (PMOS 72.1%) |
| Azziz et al., 2004, US[5] | 873 women with androgen excess | 4.7% (PMOS 82.0%) |
| AE-PCOS Society pooled data, 2012[2] | 2,601 patients from several clinic series | About 10% |
The share is higher among women with mild symptoms. According to the Endocrine Society, about half of women in the US with regular periods and a mild Ferriman-Gallwey score of 8 to 15 have idiopathic hirsutism.[1] You can learn how the score works in our guide to the Ferriman-Gallwey score.
Why does idiopathic hirsutism happen if hormones are normal?
The most likely reason is that the hair follicles are more sensitive to androgens, so normal hormone levels are enough to turn fine hair into coarse hair. The Endocrine Society explains that follicle sensitivity depends partly on how the skin itself processes androgens, especially the conversion of testosterone into the stronger hormone dihydrotestosterone (DHT) by an enzyme called 5-alpha reductase.[1] Because DHT is mostly made inside the skin, a blood test does not show how much is acting on the follicle.[3]
Researchers have proposed several mechanisms, though none is proven:
- More 5-alpha reductase activity in the skin. A 2023 review calls this the main suspected abnormality.[3] The AE-PCOS Society also names more conversion to DHT and more sensitive androgen receptors as likely explanations.[2]
- Differences in the androgen receptor gene. Some studies found differences in a part of the gene that affects how strongly the receptor responds, but other studies did not.[3]
- Testing limits. Some women may have slightly raised androgens that standard tests miss. The Endocrine Society says it is unclear whether unmeasured androgens play a role, and one study using a more precise method (mass spectrometry) lowered the testosterone cutoff.[1], [3]
- Insulin resistance. In the review authors’ own patients, 18.7% of women with idiopathic hirsutism had impaired glucose tolerance, a stage before type 2 diabetes. They suggest it is more common in women with overweight.[3]
Most of this evidence is old or comes from a small number of research groups, as the 2023 review itself acknowledges.[3]
How is idiopathic hirsutism diagnosed?
Idiopathic hirsutism is a diagnosis of exclusion: A doctor reaches it only after ruling out other causes.[3] The steps usually look like this:
- Score the hair. A doctor uses the modified Ferriman-Gallwey (mFG) score, which rates hair on 9 body areas. You can try a rough version yourself with our hirsutism self-check.
- Test androgens. The Endocrine Society recommends testing testosterone in all women with an abnormal hirsutism score, ideally in the early morning.[1] The AE-PCOS Society notes that free testosterone is more sensitive than total testosterone.[2] Reference ranges vary by lab, so compare your result with your own lab’s range. Our guide to normal testosterone levels in women explains the numbers.
- Check that you really ovulate. Regular periods are not proof of ovulation. The AE-PCOS Society says 15% to 40% of women with hirsutism have regular cycles without ovulating, and recommends confirming ovulation with a progesterone blood test in the second half of the cycle or temperature charts.[2] If you do not ovulate, the diagnosis is more likely PMOS.
- Rule out NCAH. A morning blood test for 17-hydroxyprogesterone screens for non-classic congenital adrenal hyperplasia (NCAH), an inherited adrenal condition. The Endocrine Society suggests this screening in women with raised androgens; the AE-PCOS Society says screening depends on how common NCAH is locally.[1], [2]
- Other tests if needed. An ovarian ultrasound may be used, and prolactin is measured if periods are irregular or there is nipple discharge.[2] See how hirsutism is diagnosed for the full list.
If your hirsutism is mild, your periods are regular and your testosterone is normal, the Endocrine Society says further testing is only needed if there are other signs of a hormonal disorder.[1]
Idiopathic hirsutism vs PMOS vs NCAH: what is the difference?
The main difference is in blood tests and ovulation: Idiopathic hirsutism has normal androgens and normal ovulation, PMOS usually involves irregular ovulation and often raised androgens, and NCAH shows a raised 17-hydroxyprogesterone level. PMOS, previously called polycystic ovary syndrome (PCOS), was renamed polyendocrine metabolic ovarian syndrome in May 2026.[6]
| Idiopathic hirsutism | PMOS (formerly PCOS) | NCAH | |
|---|---|---|---|
| Androgen levels | Normal[1] | Often raised[7] | Often raised[1] |
| Ovulation and periods | Regular, ovulatory[2] | Often irregular or absent[7] | Can be irregular[11] |
| Ovaries on ultrasound | Normal (strict definition)[2] | Often polycystic-looking[7] | Not needed; diagnosis is by blood test[1] |
| Key test | Normal results after rule-outs | Two of three criteria, after excluding other causes[7] | Raised morning 17-hydroxyprogesterone[1] |
| Share among women seen for androgen excess (Italian clinic study)[4] | 7.6% | 72.1% | 4.3% |
| First-line treatment for hair | Pill and/or hair removal[1] | Pill and/or hair removal[1] | Same as PMOS[1] |
For a closer look at the most common overlap, read the difference between hirsutism and PCOS (PMOS), and for the full list of causes, see what causes hirsutism.
How is idiopathic hirsutism treated?
Idiopathic hirsutism is treated the same way as other hirsutism: Hair removal, the birth control pill, and anti-androgen medicines if needed. The Endocrine Society says that for women with mild hirsutism and no sign of a hormonal disorder, either medication or direct hair removal is a reasonable first choice.[1] Treatment is optional. If the hair does not bother you, there is no medical need to remove it.
Hair removal
Evidence: Strong The Endocrine Society suggests laser or intense pulsed light for brown or black hair and electrolysis for white or blonde hair.[1] Shaving, waxing, threading and creams are also options. Hair removal works on the hair you already have, while medicines aim to slow new growth.
Birth control pill
Evidence: Strong The Endocrine Society suggests combined oral contraceptives as first-line medication for most women with hirsutism who are not trying to get pregnant, and states that idiopathic hirsutism may respond to this treatment.[1] A 2015 Cochrane review of 157 trials, which included women with idiopathic hirsutism, found that the pill reduced hair growth, but the certainty of the evidence was low.[8]
Anti-androgens such as spironolactone
Evidence: Moderate If hair is still a problem after 6 months on the pill, the Endocrine Society suggests adding an anti-androgen.[1] In the Cochrane review, spironolactone reduced hair scores more than placebo, with low-certainty evidence.[8] The AE-PCOS Society describes a placebo-controlled trial in 40 women with PCOS or idiopathic hirsutism in which spironolactone, finasteride and flutamide all worked better than placebo.[2] Anti-androgens can harm a developing baby, so the guideline advises against using them alone unless you use reliable contraception.[1] The guideline recommends against flutamide because of liver risk.[1] Read more in our guide to hirsutism medication.
Steroids and metformin
Evidence: Limited The AE-PCOS Society reports that glucocorticoid (steroid) tablets worked less well than the pill or anti-androgens in idiopathic hirsutism.[2] The Endocrine Society advises against insulin-lowering drugs such as metformin for the sole purpose of treating hirsutism, because metformin was no better than placebo for hair scores.[1]
How long until treatment works?
Expect to wait at least 6 months. The Endocrine Society suggests a trial of at least 6 months before changing the dose or switching medicine, because hair grows slowly.[1]
What is the outlook for idiopathic hirsutism?
Idiopathic hirsutism is not dangerous in itself, because by definition no hormonal disease has been found. The main open question is whether it stays the same over time. The authors of the 2023 review suggest it may sometimes be an early stage of an androgen disorder such as PMOS, possibly triggered by insulin resistance, but they present this as a hypothesis that needs long-term studies.[3] We could not find any study that followed women with idiopathic hirsutism for many years. If your periods change or new symptoms appear, it is worth getting checked again.
When should you see a doctor?
See a doctor if the hair bothers you, especially if you also have irregular periods.[9] Seek an urgent appointment if thick, dark hair starts growing suddenly or your voice gets deeper.[9] Other warning signs are rapidly worsening hair growth, an enlarged clitoris, or periods that become irregular or stop.[1] These do not fit idiopathic hirsutism and need prompt testing.
Frequently asked questions
Can you have hirsutism with normal hormone levels?
Yes. This is what idiopathic hirsutism means. The British Association of Dermatologists notes that in 5% to 20% of affected women no underlying cause is found, and the extra hair is thought to come from follicles that are more sensitive to normal androgen levels.[10], [1]
Is idiopathic hirsutism the same as PCOS (PMOS)?
No. PMOS usually involves irregular ovulation, and often raised androgens or polycystic-looking ovaries. Idiopathic hirsutism means ovulation and androgens are normal.[2], [7] Because regular periods do not always mean ovulation, a doctor may check ovulation with a blood test before giving this diagnosis.[2]
Does idiopathic hirsutism respond to treatment?
Yes. It is treated like other hirsutism, and the Endocrine Society notes it may respond to the birth control pill.[1] Clinical trials of anti-androgens have included women with idiopathic hirsutism and showed improvement compared with placebo, though most trials were small.[8], [2]
Is idiopathic hirsutism genetic?
It may run in families, but we found no studies that measure how strongly idiopathic hirsutism specifically is inherited. The AE-PCOS Society notes that a family history of androgen excess is common in women with hirsutism without a serious underlying disease.[2] Read more in is hirsutism hereditary.
Should I get tested again later?
Consider it if things change. Experts have suggested that some women first diagnosed with idiopathic hirsutism may later show signs of PMOS, but this has not been proven.[3] New irregular periods, rising hair growth or other new symptoms are reasons to go back to your doctor.
Key takeaways
- Idiopathic hirsutism means male-pattern hair growth with normal androgen levels and normal ovulation, after other causes are ruled out.
- It accounts for about 5% to 20% of women with hirsutism and about half of women with mild hirsutism and regular periods.
- The likely cause is more sensitive hair follicles, possibly through higher 5-alpha reductase activity in the skin.
- Diagnosis requires checking androgens, confirming ovulation and ruling out NCAH.
- Treatment is the same as for other hirsutism: Hair removal, the pill and anti-androgens, with at least 6 months to judge results.
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
- Escobar-Morreale HF, Carmina E, Dewailly D, et al. Epidemiology, diagnosis and management of hirsutism: a consensus statement by the Androgen Excess and Polycystic Ovary Syndrome Society. Hum Reprod Update. 2012;18(2):146-170. PubMed 22064667
- Unluhizarci K, Hacioglu A, Taheri S, Karaca Z, Kelestimur F. Idiopathic hirsutism: Is it really idiopathic or is it misnomer? World J Clin Cases. 2023;11(2):292-298. PubMed 36686351
- 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, 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
- 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
- van Zuuren EJ, Fedorowicz Z, Carter B, Pandis N. Interventions for hirsutism (excluding laser and photoepilation therapy alone). Cochrane Database Syst Rev. 2015;(4):CD010334. Link
- NHS. Excessive hair growth (hirsutism). Accessed October 2026. Link
- British Association of Dermatologists. Hirsutism (BAD Patient Hub). Accessed October 2026. Link
- 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
This article is for education and is not medical advice. Talk to a doctor about diagnosis and treatment.