• Evaluation of reproductive-age patients with irregular menses (oligomenorrhea or amenorrhea).
• Workup for signs of hyperandrogenism (hirsutism, acne, androgenetic alopecia).
• Infertility evaluation related to anovulation.
• Differentiating PCOS from other endocrine disorders (e.g., NCCAH, Cushing’s, thyroid dysfunction).

• Oligo- and/or Anovulation: Menses at intervals >35 days or <9 per year.
• Clinical and/or Biochemical Hyperandrogenism: Modified Ferriman-Gallwey score ≥4–6 or elevated total/free testosterone.
• Polycystic Ovaries (on Ultrasound): ≥12 follicles (2–9 mm) in either ovary and/or increased ovarian volume (>10 mL).

The Rotterdam criteria allow for four distinct PCOS phenotypes: Phenotype A (Full: Hyperandrogenism + Ovulatory dysfunction + PCO), B (Non-PCO), C (Ovulatory), and D (Non-hyperandrogenic). Phenotypes A and B carry the highest risk for metabolic syndrome and insulin resistance.

• Clinical hirsutism is a more reliable marker of hyperandrogenism than biochemical testing in many patients.
• Anti-Müllerian Hormone (AMH) is often elevated in PCOS but is not yet formally part of the Rotterdam diagnostic criteria.
• Polycystic ovaries (PCO) alone do NOT constitute PCOS; approximately 20% of normo-ovulatory women have PCO morphology.

• Assess for metabolic comorbidities: 2-hour OGTT (preferred over HbA1c) and fasting lipid panel.
• Lifestyle Modification: First-line for all BMI categories to improve ovulatory function and metabolic profile.
• Cycle Regulation: Combined Oral Contraceptive Pills (COCPs) are first-line to prevent endometrial hyperplasia.
• Hyperandrogenism: COCPs +/- Spironolactone (wait 6 months for effect; ensure contraception as it is teratogenic).
• Infertility: Letrozole is now first-line for ovulation induction (superior to Clomiphene in PCOS).

Prior to 2003, the NIH criteria (1990) required both hyperandrogenism and oligo-ovulation. The Rotterdam meeting, held in the Netherlands, recognized that excluding PCO morphology missed a large cohort of women with similar metabolic and reproductive risks, leading to the current broader definition.

The criteria represent a rare consensus between the European Society of Human Reproduction and Embryology (ESHRE) and the American Society for Reproductive Medicine (ASRM), aiming to standardize PCOS research and clinical care worldwide.