Intrauterine microdialysis reveals cycle-dependent regulation of endometrial insulin-like growth factor binding protein-1 secretion by human chorionic gonadotropin

Objective: To investigate whether hCG may directly influence endometrial differentiation and function. Design: Controlled clinical study. Setting: Tertiary university center. Patient(s): Fifty-six women with infertility. Intervention(s): An intrauterine microdialysis device (IUMD) was developed that consisted of two balloon catheters connected by microdialysis tubing (molecular weight cutoff: 2.000 kDa). The IUMD was inserted into the uterine cavity and perfused with saline for 3 hours. In 45 women, urinary hCG was then added for 5 hours. Eleven women underwent an identical procedure but without the application of hCG. Main Outcome Measure(s): The response of the endometrium was assessed by measuring IGFBP-1 in the perfusate. Result(s): Intrauterine secretion of IGFBP-1 was strictly confined to the late secretory phase ( ! 10 days after the beginning of the LH peak). This time point marks the closing of the implantation window. The application of bCG did not affect intrauterine IGFBP-1 levels before day 10 but induced a significant decrease of intrauterine IGFBP-1 levels thereafter. There was no significant change of intrauterine IGFBP-1 levels in the controls. Conclusion(s): Intrauterine microdialysis allows a dynamic assessment of endometrial paracrine function in vivo. Human chorionic gonadotropin may be involved in the mechanisms regulating endometrial receptivity.