Polycystic ovarian syndrome (PCOS) is known as one of the most frequent endocrine diseases in women worldwide. However, this term does not completely capture the diversity of clinical signs associated with this syndrome e.g., menstrual irregularity and clinical features of androgen excess, which are though commonplace in women with PCOS, they are not included under the definition of PCOS, limited to polycystic ovarian morphology (PCOM). Utilizing the most globally accepted criterion used today in the diagnosis of PCOS, the authors of this article review and discuss the historical and current context of evidence as well as their limitations. This review addresses the phenotypic approach and age-dependent aspects of PCOS in adolescents, adult and peri/postmenopausal women, as presented in the NIH (1990, 2012), Rotterdam (2003), AE-PCOS Society (2006) consensuses and in the latest evidence-based international guideline (2018). Global data on the epidemiology of PCOS, including prevalence and distribution of polycystic ovarian syndrome phenotypes, is also analyzed in the article. Lastly, the authors discuss the importance and current need to perform more epidemiological studies focused on PCOS.

Introduction: Polycystic ovary syndrome (PCOS) is a hormonal and metabolic disorder affecting 5 to 20% of reproductive-aged women worldwide that results in androgen excess, menstrual dysfunction and oligo-ovulatory subfertility, with increased risks for type 2 diabetes, endometrial adenocarcinoma, and potentially vascular disease, among other morbidities. PCOS is a complex genetic trait with strong heritability accounting for as high as 70% of the development of the disorder. Areas covered: The authors summarize the historical and recent findings of genetic studies of PCOS, such as familial studies, twin studies, and molecular genetic studies, including the results of recent genome wide associated studies. PubMed, Medline and Embase database were used to search relevant articles. Included studies were predominately conducted in Asia, North Africa, North America, and Europe. Expert commentary: Current studies aim to establish the role and function of identified genes; such efforts could serve as potential platforms for novel diagnostic and treatments for PCOS patients. The etiology of PCOS will be better understood as more data is gathered systematically, subjects are better phenotyped larger populations are recruited, and a better understanding of the role of genetic architecture, genetic variation, epigenetics, and gene-gene, gene-environment, and gene-phenotype interaction is obtained.