The Rotterdam criteria (2003) require the presence of at least 2 of 3 features for PCOS diagnosis: (1) oligo-ovulation or anovulation, (2) clinical and/or biochemical hyperandrogenism, and (3) polycystic ovarian morphology on ultrasound (≥ 12 follicles measuring 2-9 mm per ovary or ovarian volume > 10 mL), after exclusion of other etiologies. This creates four phenotypic presentations: Phenotype A (all three criteria — classic, most metabolically severe), Phenotype B (hyperandrogenism + anovulation without polycystic morphology), Phenotype C (hyperandrogenism + polycystic morphology with regular cycles — ovulatory PCOS), and Phenotype D (anovulation + polycystic morphology without hyperandrogenism — mildest metabolic profile). All phenotypes require exclusion of thyroid disease, hyperprolactinemia, non-classic CAH, Cushing syndrome, and androgen-secreting tumors.