Phenotypes A, B, C, D

Why phenotypes?

PCOS is not a uniform condition. According to the Rotterdam criteria, diagnosis requires 2 of 3 criteria: oligo-anovulation (OA), hyperandrogenism (HA), and polycystic ovarian morphology (PCOM). The different combinations of 2 criteria (or all 3 for the complete phenotype) define 4 phenotypes with very different clinical profiles.

Knowing your phenotype is clinically useful: it guides treatment choices, predicts metabolic risk, and informs fertility prognosis.

Phenotype A — Full classic

Criteria: OA + HA + PCOM (all 3 criteria present)

This is the most metabolically severe phenotype, associated with the highest risk of insulin resistance, dyslipidaemia, and metabolic syndrome. Hyperandrogenism is often marked (hirsutism, acne). Cycles are irregular or absent. It is also the most commonly diagnosed phenotype.

Phenotype B — Classic without PCOM

Criteria: OA + HA (without the ultrasound criterion)

A severe clinical picture similar to phenotype A, but pelvic ultrasound does not show polycystic morphology (or the scan was not performed with a high-resolution probe). Metabolic risk remains high. Some people with this phenotype have normal or low AMH.

Phenotype C — Ovulatory

Criteria: HA + PCOM (with regular cycles)

This is the mildest phenotype metabolically. Cycles are regular (ovulation present), but there is hyperandrogenism (biochemical or clinical) and polycystic ovarian morphology. This phenotype is often underdiagnosed because regular cycles are incorrectly taken to rule out PCOS. Long-term cardiovascular risk exists but is lower than in phenotypes A or B.

Phenotype D — Normo-androgenic

Criteria: OA + PCOM (without hyperandrogenism)

This phenotype can appear fertility-friendly but with very irregular cycles. The absence of hyperandrogenism makes it hormonally different from phenotypes A/B/C, but the impact on fertility and cycles is similar. This phenotype is excluded by the NIH 1990 and AES 2006 criteria — which explains the debate between classification systems.

Summary table

Key takeaways

• 4 phenotypes based on which Rotterdam criteria are present
• Phenotype A most severe metabolically, C the mildest
• Phenotype C often underdiagnosed (regular cycles)
• Phenotype D excluded by NIH 1990 and AES 2006 criteria
• Phenotype guides treatment selection and monitoring