Influence of corpus luteum age on the steroidogenic response to exogenous human chorionic gonadotropin in normal cycling women

OBJECTIVE: The null hypothesis of this study is that the patterns of steroid secretion exhibited by the human corpus luteum in response to exogenous human chorionic gonadotropin stimulation are independent of corpus luteum age at the time of treatment. STUDY DESIGN: Twenty-five normally cycling women in whom the midcycle urinary luteinizing hormone surge (luteal day 0) was identified and from whom blood samples were obtained daily from cycle day 11 until menses were prospectively randomized to receive no treatment (group I, n = 5) or exogenous human chorionic gonadotropin 5000 IU administered intramuscularly on luteal day 0 (group II, n = 5), +4 (group III, n = 5), + 8 (group IV, n = 5), or + 12 (group V, n = 5). Serum concentrations of estrone, estradiol, progesterone, 17-hydroxyprogesterone, and androstenedione were measured by specific radioimmunoassays in all subjects; serum human chorionic gonadotropin concentrations were determined by immunoradiometric assay in treated subjects. RESULTS: Serum human chorionic gonadotropin levels (mean ± SEM) were virtually identical among treatment groups (p > 0.05). Luteal phase duration (mean ± SEM) was prolonged (p < 0.05) only in group V (18.4 ± 0.5 days) compared with untreated subjects (group 113.8 ± 0.7 days). In all groups estrone and 17-hydroxyprogesterone concentrations closely paralleled those of estradiol and progesterone, respectively. Steroid data and progesterone/estradiol ratios (mean ± SEM) in groups I and II were indistinguishable and were combined (control, n = 10). Group III subjects exhibited patterns of steroid secretion similar to groups I and II, although progesterone was moderately increased after human chorionic gonadotropin treatment. In groups IV and V, progesterone increased (p < 0.05) 1 day after human chorionic gonadotropin and remained elevated for 5 to 6 days; a 4-day rise (p < 0.05) in estradiol began 3 days after treatment, and androstenedione rose modestly in parallel. Progesterone/estradiol ratios in groups III through V increased (p < 0.05) approximately twofold after human chorionic gonadotropin treatment and remained elevated for 4 to 5 days. CONCLUSION: The human corpus luteum exhibits distinct age-dependent patterns of steroid secretion in response to exogenous human chorionic gonadotropin stimulation, an observation that may have clinical implications regarding the empirical use of exogenous human chorionic gonadotropin in support of luteal function.