Increased expression of VEGF and angiopoietin 1 and 2 (ANGPT1/2) in the eutopic endometrium causes dysregulated angiogenic activity [38], and structural and/or functional differences in the eutopic endometrium may play a role in endometrial cells entering the peritoneal cavity to form endometriosis lesions [39, 40]. Here, ANGPT1 is linked to endometriosis.