Corpus luteum response to exogenous HCG during the mid-luteal phase of themenstrual cycle

OBJECTIVE To assess a range of exogenous HCG regimes designed to simulate t he endocrine environment occurring in biochemical, single and multiple preg nancies and to study the response of the corpus luteum to those regimes. DESIGN Prospective clinical study. PATIENTS Twenty-five normally cycling women aged 24-35 years were given one of four regimes of HCG injections designed to mimic the HCG concentrations found following spontaneous implantation. Regimes A, B, C and D were desig ned with starting HCG doses of 60, 140, 250 and 1000 iu, respectively. The daily HCG injections were then increased to give a doubling concentration e very 30 h for regime A, every 27 h for regime B, every 24 h for regimes C a nd D. HCG administration was started on either days 7 or 8 after the LH pea k. MEASUREMENTS Plasma HCG and progesterone concentrations, RESULTS Subjects given regime A failed to demonstrate any rescue of the cor pus luteum despite low-detectable amounts of HCG in the circulation equival ent to those seen in some biochemical pregnancies. In contrast, subjects gi ven regimes B and C demonstrated prompt increases in progesterone secretion immediately after the first HCG injection achieving HCG and progesterone c oncentrations in plasma similar to those seen in normal singleton pregnanci es. Subjects given regime D also showed rapid rescue of the corpus luteum b ut this time achieved plasma HCG concentrations in the range normally seen in multiple pregnancies. All subjects in regimes a, C and D secreted signif icantly higher amounts of progesterone than those in regime A (P<0.001). Ho wever, despite the greater amounts of HCG used in regime D, the amount of p rogesterone produced was not significantly different from regimes B or C, CONCLUSIONS The exogenous HCG regimes used in this study successfully mimic ked the hormonal environment found in biochemical, single and multiple preg nancies acid elicited appropriate corpus luteum responses.