Transforming growth factor β (TGF-β) is abundantly expressed in the endometrium and is secreted by the endometrial cells and macrophages into the uterine fluid, where its interactions with pre-embryonic implantation are suspected.(8) TGF-β secretion in the peritoneal fluid of women suffering from endometriosis suggests that it may be critical in the establishment and/or maintenance of endometriosis.(9). Here, TGFB1 is linked to endometriosis.