Introduction: Determinants of polycystic ovary syndrome

The polycystic ovary syndrome (PCOS) is recognized as one of the most common endocrine abnormalities of humans, with global prevalences so far generally 5%–15%. Overall, the disorder appears to be an ancient complex genetic trait, perhaps dating at least 50,000 years ago. The phenotype of PCOS can be subdivided into four different types. Phenotype A and B (hyperandrogenism + ovulatory dysfunction, with [A] and without [B] polycystic ovarian morphology [PCOM], respectively) can be considered to represent the “classic” form of the disorder. Phenotype C is the so-called “ovulatory” PCOS (hyperandrogenism + PCOM only). And phenotype D is often referred to as “nonhyperandrogenic” PCOS (ovulatory dysfunction + PCOM only). The different phenotypes vary in the degree to which they are associated with an increased risk for metabolic dysfunction and reproductive complications. There are a number of determinants of the epidemiology (prevalence) and presentation (phenotype) of PCOS, including environmental (e.g., socioeconomic, geographic, toxicologic, life-style, and dietary) and genetic (e.g., gene variants, epigenetic, and race/ethnicity) factors. Finally a better understanding of the evolutionary determinants of PCOS has the potential for providing additional insight into those factors determining the etiology, prevalence, and persistence of a disorder that appears to be, superficially at least, an evolutionary paradox.