PCOS phenotypes explained: Rotterdam types A, B, C and D compared
PCOS is not one single condition that looks the same in every woman. Two women can both have PCOS, yet one has irregular periods, thick facial hair and polycystic ovaries on the scan, while the other has regular periods and only acne and hair thinning. These different combinations are called phenotypes. Knowing your phenotype tells you how likely you are to have insulin resistance, how fertility may be affected, and which treatment should come first.
The Rotterdam criteria in simple words
PCOS is diagnosed using the Rotterdam criteria (2003), which are still used in the 2023 International PCOS Guideline. You need 2 of these 3 features, after other causes such as thyroid disease and high prolactin have been ruled out:
- Irregular or absent ovulation: periods that come less than 8 times a year, cycles longer than 35 days, or no periods at all
- Hyperandrogenism: signs of high male-type hormones, either clinical (excess facial or body hair, acne, scalp hair thinning) or biochemical (raised testosterone on a blood test)
- Polycystic ovaries: many small follicles or an enlarged ovary on ultrasound (or a raised AMH level in adults)
Depending on which 2 or 3 features you have, you fall into one of four phenotypes: A, B, C or D.
The 4 Rotterdam phenotypes side-by-side: because treatment differs
The table below compares the four phenotypes on 9 clinical features.
| Feature | Phenotype A (Classic) | Phenotype B (H+O) | Phenotype C (Ovulatory) | Phenotype D (Normoandrogenic) |
| Hyperandrogenism | Yes (clinical + biochemical) | Yes | Yes | No |
| Ovulation dysfunction | Yes (oligo/anovulation) | Yes | No, ovulates regularly | Yes |
| Polycystic ovaries on ultrasound | Yes | No, normal ovaries | Yes | Yes |
| Metabolic risk (T2DM/CV) | Highest | High | Intermediate | Lowest |
| Prevalence in PCOS | About 60% | About 7% | About 15% | About 18% |
| Fertility challenges | Common | Common | Uncommon | Common |
| Priority intervention | Lifestyle + metformin + COCP | Lifestyle + metformin | Anti-androgen +/- COCP | Cyclical progesterone / COCP |
| If seeking pregnancy | Weight loss + letrozole | Letrozole + metformin | Usually spontaneous | Letrozole |
| Primary specialist | Endocrinologist | Endocrinologist | Gynecologist | Gynecologist |
Prevalence figures vary between studies and depend on whether the group studied was recruited from clinics or from the general population.
Phenotype A: classic PCOS
Phenotype A has all three features: irregular ovulation, high androgens and polycystic ovaries. It is the form most often described in textbooks and the one most women picture when they hear the word PCOS. Typical signs are infrequent periods, acne, excess hair on the face, chin or abdomen, and often weight gain around the waist.
This group has the highest metabolic risk. Insulin resistance is common, so the risk of prediabetes, type 2 diabetes, fatty liver and high cholesterol is greater, and these should be checked early. Because ovulation is affected, getting pregnant may take longer. Treatment usually combines lifestyle change, metformin or inositol, and a combined pill to regulate periods and lower androgens. If pregnancy is the goal, weight loss and letrozole are the usual route.
Phenotype B: high androgens with irregular ovulation
Phenotype B has high androgens and irregular ovulation, but the ovaries look normal on ultrasound. It can be missed when a doctor relies only on the scan, even though it behaves almost like phenotype A. Metabolic risk is high, so blood sugar, lipids and blood pressure need the same attention.
Treatment follows the same lines as phenotype A: lifestyle change and metformin, with a combined pill or anti-androgen for hair and acne. For women trying to conceive, letrozole with metformin is a common approach.
Phenotype C: ovulatory PCOS
Phenotype C means you ovulate regularly and your periods look normal, yet you have signs of high androgens (acne, hirsutism, hair thinning) and polycystic ovaries on ultrasound. Because the cycle is regular, this type is often missed or dismissed as just skin and hair problems.
Metabolic risk sits in the middle, and fertility is usually less affected than in the other types, so many women conceive without treatment. The main goal is to control androgen symptoms with an anti-androgen such as spironolactone, with or without a combined pill. Contraception is essential while on an anti-androgen.
Phenotype D: normoandrogenic PCOS
Phenotype D means irregular ovulation and polycystic ovaries, but no clinical or blood-test evidence of high androgens. Diagnosing it needs extra care because several other conditions, such as thyroid disease, high prolactin and hypothalamic causes of missed periods, can look the same and must be excluded first.
This group generally has the lowest metabolic risk, but irregular ovulation still means fertility may need support and the uterine lining needs protection from long gaps between periods. Treatment is usually cyclical progesterone or a combined pill for cycle control, with letrozole when pregnancy is wanted.
How do you find out your phenotype?
Your phenotype is worked out by your doctor from a combination of history, examination and tests. You cannot reliably guess it from symptoms alone. A typical work-up includes:
- Cycle history over the last 12 months
- Examination for hirsutism using the modified Ferriman-Gallwey (mFG) score, where 8 or more suggests hirsutism in South Asian women, plus acne and hair thinning
- Blood tests: total and free testosterone with SHBG, DHEAS, LH and FSH, TSH, prolactin and 17-hydroxyprogesterone to rule out look-alike conditions
- Ultrasound of the ovaries, or an AMH test in adults when the scan is not suitable
- Metabolic tests whichever phenotype you have: fasting glucose or glucose tolerance test, HbA1c, fasting insulin, lipid profile and liver tests
Can your phenotype change over time?
Yes. Your phenotype is a snapshot, not a life sentence. With weight loss, treatment, and ageing, periods can become more regular, androgen levels can fall and the ovaries may look different on the scan, so a woman can move from one phenotype to another. It is sensible to review your diagnosis and risk factors every year or two rather than assuming nothing has changed.
Does your phenotype change the treatment?
The foundations are the same for every phenotype: balanced nutrition, regular physical activity, good sleep and attention to mental health. The phenotype decides what is added on top: metformin or inositol when insulin resistance is likely, a combined pill or cyclical progesterone for cycle control, an anti-androgen for hair and acne, and letrozole when pregnancy is the goal. Matching treatment to phenotype avoids both under-treatment and unnecessary medicine.
Which doctor should you see?
Women with phenotypes A and B usually benefit from an endocrinologist as the lead because of the higher metabolic risk, with a gynecologist for periods and fertility. For phenotypes C and D, a gynecologist usually leads, with an endocrinologist or dietitian added if blood sugar, weight or cholesterol are a concern. Online consultations make it easy to see both and share one care plan.
Key takeaways
- PCOS is diagnosed when 2 of 3 Rotterdam features are present: irregular ovulation, high androgens and polycystic ovaries
- The four phenotypes (A, B, C, D) differ in metabolic risk, fertility and treatment priority
- Phenotype A carries the highest metabolic risk and phenotype D the lowest
- You can have PCOS even if your periods are regular (phenotype C) or your ovaries look normal (phenotype B)
- Your phenotype can change over time, so review it periodically with your doctor
