Expression of vascular endothelial growth factors and their receptors in human endometrium from women experiencing abnormal bleeding patterns after prolonged use of a levonorgestrel-releasing intrauterine system.

BACKGROUND Menstrual bleeding disturbances are a common initial complaint among users of the levonorgestrel-releasing intrauterine system (LNG-IUS). In this study, women who experienced bleeding disturbances recurring after a previous period of problem-free use and who therefore wanted removal of their LNG-IUD were investigated. Vascular endothelial growth factors (VEGFs) and their receptors are thought to be involved in normal endometrial angiogenesis. The aim of the study was to elucidate the possible association of these VEGF and receptors with bleeding disturbances among users of LNG-IUS. METHODS Endometrial biopsies were obtained from users of the LNG-IUS who complained of bleeding disturbances (n = 17) and from women without such problems (n = 14). The endometrial expression of these VEGFs and their receptors was analysed using immunohistochemistry. RESULTS Endometrial endothelial cells from LNG-IUS users with menstrual bleeding disturbances exhibited significantly higher immunoreactivity for VEGFR-1 and VEGFR-3 than those from women without bleeding disturbances. Stromal cells showed significantly lower immunoreactivity for VEGF-A in samples from LNG-IUS users with bleeding disturbances than in those without. CONCLUSION Changes in the expression of these angiogenic growth factors and their receptors in LNG-IUS-exposed endometrium might be involved in the formation of fragile and dysfunctional blood vessels that subsequently give rise to bleeding disturbances.