Endocrine responses to gonadotrophins after LHRH agonist administration on cycle days 1-4: prevention of premature luteinization.

A treatment regime comprising an intranasally administered luteinizing hormone-releasing hormone (LHRH) agonist analogue (buserelin) on cycle days 1-4, followed by gonadotrophin administration [follicle stimulating hormone (FSH)/human menopausal gonadotrophin (HMG)] resulted in identical oestradiol (E2) responses compared with the reference method using clomiphene citrate (CC) and gonadotrophins. Immediately after analogue administration (day 4), buserelin-treated women showed short-lived elevations in serum LH and progesterone concentrations, but in the later follicular phase, the serum LH concentration was lowered compared with the controls. None of the women treated with analogue displayed elevated serum LH or progesterone concentrations at the time of injection of human chorionic gonadotrophin. In the early luteal phase, these women had higher serum levels of progesterone and higher progesterone to E2 ratios than the controls, but the length of the luteal phase was slightly shortened. Hence, in hyperstimulated cycles, 4-day treatment with buserelin caused profound endocrinological changes: namely, short-term rescue of the corpus luteum, prevention of an endogenous LH rise and premature luteinization and increased progesterone production in the early luteal phase.