It was also found that the peritoneal fluid of endometriosis patients contains high concentrations of various OS markers such as MDA, pro-inflammatory cytokines (interleukin-6 (IL-6), TNF-α, transforming growth factor- β (TGF-β) and IL-1β), angiogenic factors (IL-8 and VEGF), neural growth factor and oxidized LDL (ox-LDL) (155, 156). This evidence concerns the gene IL6 and endometriosis.