P2X (purinergic X) receptors, are another increased nociceptor in endometriosis which can be activated by extracellular ATP [87].As mentioned above, aberrant expression of ERα and ERβ in macrophages of endometriosis is correlated with the function of inflammatory cytokines, indicating the active role of estrogen in the secretion of inflammatory cytokines from macrophages [31]. The gene discussed is ESR2; the disease is endometriosis.