Polycystic ovary syndrome (PCOS) affects 8–13% of women. The Rotterdam diagnostic criteria include polycystic ovarian morphology (PCOM) on ultrasound, but given recognized challenges, serum anti-Müllerian hormone (AMH) is proposed as an alternative. To inform international PCOS guidelines, a systematic review was completed. Key identified gaps include large international studies in well-defined populations across the lifespan, clustering of AMH with PCOS features, relationships to long-term health outcomes, and improved quality, assay standardization, and sample handling, all needed to determine cut offs. Here we identify research priorities to address these gaps and enhance AMH utility in PCOS. Once issues are addressed, AMH levels could replace more costly and less accessible ultrasound in PCOS diagnosis.