The optimum time for exogenous human chorionic gonadotropin to rescue the corpus luteum

Purpose: Our purpose was to study the optimum time to administer exogenous human chorionic gonadotropin (hCG) to rescue the human corpus luteum during the luteal phase of normal menstrual cycles. Methods: Groups of normally cycling women were given 4-day regimes of exoge nous hCG by daily injection beginning 4 (Group A), 8 (Group B), and 12 (Gro up C) days after the midcycle luteinizing hormone surge. The hCG regime use d was designed to mimic hCG levels following a spontaneous implantation. Al l subjects acted as their own controls in a preceding normal menstrual cycl e. Results: Group A subjects exhibited patterns and levels of the control cycl es throughout the normal luteal phase. In contrast, subjects in both Group B and Group C demonstrated a rapid and sustained increase in progesterone p roduction following the hCG injections. Furthermore, subjects in Group B ac hieved the highest mean peak progesterone secreted was significantly higher than in the control cycles (P < 0.05). Although the mean luteal-phase leng th was suboptimal, with a delayed rise in salivary progesterone. Conclusions: These data show that the qualitative and quantitative response of corpus luteum to an early pregnancy-type hCG signal is maximal around t he midluteal phase, coincident with the time of implantation.