Variations of luteinizing hormone serum concentrations after exogenous human chorionic gonadotropin administration...

Changes in luteinizing hormone (LH), estradiol, and progesterone (P) serum levels before and after preovulatory administration of human chorionic gonadotropin (hCG) were assayed in 30 patients stimulated with clomiphene citrate (CC) and human menopausal gonadotropin (hMG) and compared with LH variations in 43 patients submitted to pharmacological hypophysectomy with a gonadotropin-releasing hormone agonist (GnRH-a) and stimulation with hMG. In CC + hMG-treated patients, an endogenous LH surge occurred systematically 4.25 +/- 2.75 hours after hCG injection. Multiparametric analysis indicated an inverse correlation between the delay in the initial rise of the LH surge and the increase in P levels during the 6 hours after hCG administration. Gonadotropin-releasing hormone agonist + hMG treatment did not lead to an LH surge after hCG but to a significant fall in LH levels. Thus, exogenous hCG, administered before ovulation, induces an endogenous LH surge if pituitary function is not blocked by a GnRH-a, probably through an increase in P secretion.