Background: Leptin has been proposed as a biomarker for endometriosis. Previous studies have shown mixed results. The aim of this study was to compare peritoneal fluid (PF) leptin concentrations between patients with and without endometriosis in a cohort of sufficient size to detect a significant difference. Methods: Patients of reproductive age undergoing laparoscopic surgery for endometriosis or other benign indications in the Department of Gynecology, University of Bern between 2007 and 2018 were recruited. Peritoneal fluid was aspirated at laparoscopy and the concentration of leptin measured by Enzyme-linked immunosorbent assay (ELISA). Leptin concentrations were compared between patients with and without endometriosis by an analysis of covariance. Results: 1054 patients were included in the analysis, of which 653 patients were diagnosed with endometriosis. Leptin concentrations strongly correlated with body mass index (BMI) (R²=0.313; F (1,1033)=470.73, p<0.001). After correcting for BMI, no difference was found in leptin concentrations between patients with and without endometriosis (p=0.051). Conclusion: Peritoneal fluid leptin concentrations correlated with BMI, but did not significantly differ between patients with and without endometriosis. This suggests leptin does not represent a viable biomarker for endometriosis.

Leptin, Endometriosis, Peritoneal fluid, Biological marker, BMI, Cycle phase