Endocrine composition of follicular fluid comparing human chorionic gonadotrophin to a gonadotrophin-releasing hormone agonist for ovulation induction.

Concentrations of inhibin, oestradiol and progesterone were determined in pre-ovulatory follicular fluid from 16 women undergoing in-vitro fertilization and embryo transfer treatment. A prospective randomized design was used such that ovulation was induced in eight women with human chorionic gonadotrophin (HCG) (9000 IU), and in eight women with an endogenous surge of luteinizing hormone (LH) and follicle stimulating hormone (FSH) caused by a single injection of gonadotrophin-releasing hormone agonist (GnRHa). Inhibin was measured by an enzyme-linked immunosorbent assay, and oestradiol and progesterone were measured by radio-immunoassay. Concentrations of inhibin and progesterone are significantly higher in follicular fluids collected after ovulation induction with HCG compared with ovulation induction with GnRHa (P < 0.001, P < 0.02, respectively). Concentrations of oestradiol were similar in the two groups. This study shows that the method by which ovulation is triggered significantly affects the micro-environment of the oocyte just prior to ovulation. The results indicate that HCG causes a prolonged luteotrophic effect well before ovulation, compared to an endogenous surge of gonadotrophins caused by GnRHa, and suggest that follicular maturation with an endogenous surge of gonadotrophins may be closer to the natural cycle than those cycles in which HCG is administered for ovulation induction. In addition, this study shows that the concentrations of inhibin and progesterone in follicular fluid may be valuable parameters in assessing the midcycle LH surge requirements for induction of ovulation.