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 exogenous hCG by daily injection beginning 4 (Group A), 8 (Group B), and 12 (Group C) days after the midcycle luteinizing hormone surge. The hCG regime used was designed to mimic hCG levels following a spontaneous implantation. All subjects acted as their own controls in a preceding normal menstrual cycle.
RESULTS: Group A subjects exhibited patterns and levels of salivary progesterone concentration similar to those seen in the control cycles throughout the normal luteal phase. In contrast, subjects in both Group B and Group C demonstrated a rapid and sustained increase in progesterone production following the hCG injections. Furthermore, subjects in Group B achieved the highest mean peak progesterone concentrations and the total amount of salivary progesterone secreted was significantly higher than in the control cycles (P < 0.05). Although the mean luteal-phase length was greatest in Group C, the response of the corpus luteum 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 the midluteal phase, coincident with the time of implantation.