P2RX3 and endometriosis: In women with endometriosis, the frequency and score of P2X3 expression in eutopic endometrium were 74.1% (20/27) and 3.3±1.4 in women with pain (n = 27), and 33.3% (7/21) and 2.0±1.9 in women no pain (n = 21), respectively.