SPP1 and endometriosis: Women with endometriosis may also have reduced endometrial receptivity, as evidenced by the reduced expression of various endometrial receptivity markers [38]: Reduced endometrial expression of the avb integrin (a molecule important for embryo attachment at the time of implantation) has been demonstrated in women with endometriosis [39], as well as reduced levels of biomarkers of implantation, namely glycodelin A (GdA), osteopontin (OPN), lysophosphatidic acid receptor 3 (LPA3), and HOXA10 [40].