TIMP1 and endometriosis: Because of the necessity for balance between MMPs and TIMPs, it is not surprising that a differential expression of MMPs and TIMPs is associated with the pathophysiology of endomiolysis and the imbalance between the secretion of MMP-9 and its natural inhibitor TIMP-1 in the culture milleu of endometriosis tissue probably reflects the increased ability of this tissue in vivo to cleave the extracellular matrix, thereby facilitating the ectopic implantation of endometrial growth.