Erythropoietin concentrations are elevated in the peritoneal fluid of women with endometriosis

Erythropoietin (Epo) is an important regulator of erythropoiesis and stimulates the proliferation of early erythroid precursors as well as the differentiation of late erythroid precursors of the erythroid lineage. However, recent studies have indicated that Epo also has angiogenic properties and plays an important role in the oestrogen-dependent cyclical angiogenesis within the mouse uterus. It was therefore postulated that Epo may be an important angiogenic factor in endometriosis. In order to address this hypothesis the concentration of Epo in peritoneal fluid (PF) was determined in patients with or without endometriosis. PF was collected from patients with endometriosis (n = 42) or without endometriosis (n = 18). Detectable concentrations of Epo were found in all PF samples analysed. The concentration of Epo in PF from patients with endometriosis was significantly higher than that in the control group (13.1 ± 1.2 mIU/ml versus 7.2 ± 0.7 mIU/ml, mean ± SE respectively, P < 0.01). Furthermore, in patients with endometriosis the Epo concentrations in PF from patients with stage I disease (n = 17, 16.6 ± 3.0 mIU/ml) were significantly higher than those with stage II (n = 8, 10.7 ± 1.2 mIU/ml, P < 0.03), III (n = 13, 8.4 ± 1.0 mIU/ml, P < 0.01), IV disease (n = 7, 7.5 ± 1.0 mIU/ml, P < 0.01). These data suggest that Epo may play a role in the pathogenesis of endometriosis particularly in the initiation of the disease.