MMP9 and endometriosis: It is unclear whether serum NGAL levels change in the case of endometrioma, and while one of the two studies in the literature reported no difference, the other indicated that the NGAL level was higher in the endometrioma group (8, 9) On the other hand, recent articles have increasingly focused on the role of MMP-9 in reproductive health, particularly in the context of endometriosis and infertility.