Background: A recent prospective randomized study from our group compared GnRH agonist (0.5 mg buserelin) and hCG (10,000 IU) for triggering of ovulation following a flexible antagonist protocol. The agonist group showed a poor reproductive outcome despite luteal phase support with progesterone and estradiol (E(2)). In the present prospective observational study, the health status of follicles from the above study was monitored by analysing the hormonal content of frozen/thawed follicular fluid samples. The aim was to test whether the poor reproductive outcome could be related to a defective pre-ovulatory follicular maturation resulting in oocytes with a compromised developmental competence.
Methods: Hormone concentrations were measured in two individual follicular fluid samples from each of 32 women receiving buserelin and 37 receiving hCG, thus representing a subset of the follicles retrieved.
Results: Follicular fluid levels of LH in the agonist group as compared with the hCG group was 11.1 +/- 0.5 versus 3.6 +/- 0.3 IU/l (mean +/- SEM; P < 0.001); FSH, 6.3 +/- 0.6 versus 3.3 +/- 0.2 IU/l (P < 0.001); hCG, not determined versus 139+/-8 IU/l; E(2), 1.9 +/- 0.2 versus 1.8 +/- 0.2 micromol/l (P > 0.10); progesterone, 70 +/- 4 versus 93 +/- 6 micromol/l (P < 0.001); inhibin-A, 36.9 +/- 3.1 versus 37.1 +/- 2.5 ng/ml (P > 0.10) and inhibin-B, 35.6 +/- 2.8 versus 40.1 +/- 3.1 ng/ml (P > 0.10). Thus, pronounced hormonal differences exist in follicular fluid, and the collective concentration of all three gonadotropins and the follicular fluid concentration of progesterone were much higher in the group of women receiving hCG for ovulation induction.
Conclusion: The study suggests that GnRH agonist results in proper pre-ovulatory follicular maturation, but the ovulatory signal--probably in synergy with the resulting pituitary down-regulation--is too low to support appropriate corpus luteum (CL) function.