TLR4 and endometriosis: As previously mentioned, intestinal microbiota imbalance can also lead to LPS leakage by increasing intestinal permeability, which activates the innate immune system through TLR4 and increases the expression of pro-inflammatory cytokines, thus promoting the occurrence and development of endometriosis (Khan et al., 2010; Bruner-Tran et al., 2013).