Inverse correlation between peritoneal fluid leptin concentrations and the extent of endometriosis

BACKGROUND: The role of leptin in reproductive processes has received increasing attention. Because leptin has intrinsic angiogenic properties, may be induced by inflammatory cytokines and induces matrix metalloproteinases, we examined peritoneal fluid (PF) leptin concentrations in women with endometriosis. METHODS: PF samples were collected from 60 women undergoing laparoscopy for endometriosis, and 18 controls undergoing tubal sterilization. Fifty of the women with endometriosis had received no prior hormonal treatment, while 10 with moderate-severe endometriosis were using GnRH agonists. RESULTS: Women with untreated endometriosis had significantly higher (mean +/- SD) PF leptin levels (34.9 +/- 7.9 ng/ml) than controls (17.9 +/- 4.1 ng/ml; P < 0.001). However, PF leptin levels were inversely correlated with the stage of disease (r = -0.62; P < 0.001). Nevertheless, women with stage III-IV endometriosis maintained significantly higher PF leptin levels (26.3 +/- 4.8 ng/ml; P < 0.001) than controls. Although PF leptin levels were significantly higher in the secretory versus proliferative phase of the menstrual cycle, they remained higher in both phases in women with untreated endometriosis. PF leptin levels in women on GnRH agonists were similar to controls. CONCLUSIONS: PF leptin levels are elevated in women with endometriosis, but inversely correlated with extent of disease. These findings suggest a potential role for leptin in the pathogenesis of peritoneal endometriosis.