GNRH1 and ovarian hyperstimulation syndrome: However, coculture of granulosa lutein cells with a GnRH-a or GnRH-ant for 48 h revealed that the concentration of vascular endothelial growth factor (VEGF) in the GnRH-ant group was significantly lower compared with the GnRH-a group, and that the VEGF level was closely associated with the manifestation of OHSS (21–23).