Serum and peritoneal fluid leptin levels in endometriosis: a systematic review and meta-analysis.

The role of leptin in the development of endometriosis has been investigated previously. However, researches on the change of leptin levels in endometriosis remains controversial. So, we aimed to clarify changes of leptin levels in patients with endometriosis and their association with the progression of endometriosis. We searched PubMed, Embase, Web of Science, and The Cochrane Library to identify relevant studies published before May 25, 2020. The detected levels of leptin in patients with endometriosis versus controls were evaluated in this meta-analysis. Eighteen studies met our inclusion criteria, five studies detected serum, nine detected peritoneal fluid and another four detected both serum and peritoneal fluid leptin levels. The overall results showed that peritoneal fluid leptin levels in patients with endometriosis was significantly higher than that in the control group, but the serum and corrected peritoneal fluid leptin levels were comparable in both groups. Subgroup analysis failed to eliminate the high degree of heterogeneity included in the studies and showed that peritoneal fluid leptin levels were significantly elevated in both early and advanced endometriosis. In conclusion, peritoneal fluid rather than serum leptin levels was elevated in patients with endometriosis, which did not seem to be related to the severity of endometriosis, but was related to body mass index.