Introduction The determinants of PCOS
Ricardo Azziz, M.D., M.P.H.
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.