Polycystic ovary syndrome (PCOS) is a complex and heterogeneous endocrine disease. The hypothesis that alterations in the microbiome are involved in the genesis of PCOS has been postulated. Aim of this review is to summarize the available literature data about the relationship between microbiome and PCOS. A search on PubMed and Medline databases was performed from inception to November 20Most of evidence has focused on the connection of intestinal bacteria with sex hormones and insulin-resistance: while in the first case, a relationship with hyperandrogenism has been described, although it is still unclear, in the second one, chronic low-grade inflammation by activating the immune system, with increased production of proinflammatory cytokines which interfere with insulin receptor function, causing IR (Insulin Resistance)/hyperinsulinemia has been described, as well as the role of gastrointestinal hormones like Ghrelin and peptide YY (PYY), bile acids, interleukin-22 and Bacteroides vulgatus have been highlighted. The lower genital tract microbiome would be affected by changes in PCOS patients too. The therapeutic opportunities include probiotic, prebiotics and synbiotics, as well as fecal microbiota transplantation and the use of IL-22, to date only in animal models, as a possible future drug. Current evidence has shown the involvement of the gut microbiome in PCOS, seen how humanized mice receiving a fecal transplant from women with PCOS develop ovarian dysfunction, immune changes and insulin resistance and how it is capable of disrupting the secondary bile acid biosynthesis. A future therapeutic approach for PCOS may involve the human administration of IL-22 and bile acid glycodeoxycholic acid.
Keywords: PCOS; insulin-resistance; microbiome; sexual hormones; therapeutic strategies.