Clinical aspects with regard to the occurrence of an endogenous luteinizing hormone surge in gonadotropin-induced normal menstrual cycles.

A decline in serum E2 the day before laparoscopy indicated that ovulation had occurred in 16 cycles stimulated with exogenous gonadotropins for the purpose of in vitro fertilization (IVF). In contrast to 18 control cycles with rising E2 values after human chorionic gonadotropin (hCG) administration and without evidence of ovulation, the onset of the endogenous luteinizing hormone (LH) surge had been initiated. From this study, it is believed that the onset of an endogenous LH surge can be identified by the terminal preovulatory E2 pattern. Further, the incidence of an endogenous LH surge in gonadotropin-induced menstrual cycles and the present clinical approach of the Norfolk IVF program to this phenomenon are discussed.