Follicle Excess and Abnormalities in Women with PCOS: Pathophysiology, Assessment and Clinical Role

The pathophysiology of polycystic ovary syndrome (PCOS) is still not fully understood but the follicle excess plays a central role, and its mechanism in the folliculogenesis are multiple. According to the Rotterdam consensus held in 2003, the polycystic ovarian morphology (PCOM) is one of the three diagnostic criteria used to define PCOS. More specifically, PCOM is defined by an excessive antral follicle count with a follicle number per ovary (FNPO) ≥12 and/or ovarian volume ≥ 10 mL. With the improvement in ultrasonographic technology, the number of follicles seen on ultrasound has increased but it remains dependent on the specific equipment and operator. Serum anti-Mullerian hormone (AMH) is nowadays known to be a valuable tool to assess the ovarian follicle content, as AMH is synthetised by all growing follicles up to the stage of small antral follicles. Serum AMH might therefore be used as a surrogate for the FNPO in the diagnosis of PCOS, but so far technical issues have prevented from making it ‘the’ marker of follicle excess. If the assessment of follicle excess is important for the diagnosis of PCOS, it is also helpful for the management of those patients and in particular for reproductive issues.