ESR1 and Infertility: All five studies investigated the relationship between endometriosis, dysbiosis, and microbiome changes [48, 56–59]; two studies explored endometriosis and the immune system, both using animal models [48, 59]; one examined infertility, dysbiosis, and the immune system [58]; and two studies assessed estrogen metabolites or estrogen receptor (ER) activity [57, 58].