Insulin-like growth factor binding proteins in peritoneal fluid of women with minimal and mild endometriosis

This prospective cohort study was carried out in a university-based infertility clinic to determine the profile of insulin-like growth factor binding proteins (IGFBPs) in patients with mild endometriosis and no obvious mechanical factor contributing to infertility. A total of 26 patients with minimal and mild endometriosis and 10 controls contributed peritoneal fluid at surgery. The variety, expression and levels of IGFBPs were determined by radio-immunoassay and Western ligand blots (WLBs) with quantitation by laser densitometer. A 27 kDa species was significantly lower and 31 kDa species tended to be lower in patients with endometriosis as determined by quantitative laser densitometer. The levels of IGFBP-3 detected by radioimmunoassay and by WLB were correlated in the control group and in the patients with endometriosis in the follicular phase but not in patients with endometriosis in the luteal phase. The level of 27 kDa species seen on WLBs did not appear to correspond to IGFBP-1 determined by radioimmunoassay and IGFBP-3 levels in luteal phase endometriosis patients also departed from values determined by radioimmunoassay. These discrepancies suggest a complex system to control levels of IGF in the peritoneum involving multiple binding proteins and proteases. The IGFBPs of patients with endometriosis may contribute to reproductive dysfunction and be able to serve as markers.