Increased concentrations of cathepsin D in peritoneal fluid from women with endometriosis

To assess the release of the proteolytic enzyme cathepsin D in endometriosis, concentrations in peritoneal fluid and serum were measured by ELISA in 54 women with (n = 33) and without (n = 21) endometriosis. Surgery was scheduled in either the proliferative or secretory phase of the menstrual cycle. The concentrations of cathepsin D in the peritoneal fluid were markedly elevated in the endometriosis patients (median 58 ng/ml, interquartile range 0-166 ng/ml) as compared to the controls (5 ng/ml, 0-86 ng/ml), especially in women with late stage disease (n = 19, stages III/IV) and in those not undergoing gonadotrophin-releasing hormone (GnRH) agonist therapy (n = 15). No significant difference was determined in cathepsin D concentrations of the serum from women with and without endometriosis. We conclude that cathepsin D is an important factor that may contribute to the pathogenesis of endometriosis, possibly by promoting digestion of extracellular matrix proteins. These results have implications for the therapeutic efficacy of GnRH agonists.