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

A treatment regime comprising an intranasally administered luteinizinghormone-releasing hormone (LHRH) agonist analogue (buserelin)on cycle days 1–4, followed by gonadotrophin administrationfollicle stimulating hormone (FSH)/human menopausal gonadotrophin(HMG)] resulted in identical oestradiol (E₂) responses comparedwith the reference method using clomiphene citrate (CC) andgonadotrophins. Immediately after analogue administration (day4), buserelin-treated women showed short-lived elevations inserum LH and progesterone concentrations, but in the later follicularphase, the serum LH concentration was lowered compared withthe controls. None of the women treated with analogue displayedelevated serum LH or progesterone concentrations at the timeof injection of human chorionic gonadotrophin. In the earlyluteal phase, these women had higher serum levels of progesteroneand higher progesterone to E2 ratios than the controls, butthe length of the luteal phase was slightly shortened. Hence,in hyperstimulated cycles, 4-day treatment with buserelin causedprofound endocrinological changes: namely, short-term rescueof the corpus luteum, prevention of an endogenous LH rise andpremature luteinization and increased progesterone productionin the early luteal phase