Induction of maturation of cumulus-oocyte complex by gonadotropin-releasing hormone analog is associated with lower progesterone secretion.

Induction of ovulation by CG in women subjected to in vitro fertilization and embryo transfer results in maturation of the cumulus-oocyte complex (COC) in terms of oocyte meiotic maturation, cumulus mucification, and an increase in progesterone (P4) secretion. Recently an alternative approach, in which the ovulatory processes are induced by the administration of GnRH analog (GnRHa), has resulted in COCs yielding viable embryos. In the present study the effect of GnRHa administration on oocyte meiotic maturation and cumulus cell steroidogenesis was evaluated in 27 women undergoing ovarian stimulation with gonadotropin for the purpose of in vitro fertilization and embryo transfer. In GnRHa- or CG-treated women, 79.5 +/- 4.2% and 72.0 +/- 8.4% of the oocytes, respectively, manifested the first polar body. The percentages of atretic oocytes and of oocytes failing to resume meiosis were 5.8 +/- 2.1% and 6.0 +/- 2.4%, respectively, in GnRHa-treated women, and were 9.3 +/- 4.7% and 7.9 +/- 4.1%, respectively, in CG-treated women. P4 was secreted in high quantity in human cumulus cells (CCs) during a 7-day culture period. However, in CCs collected from GnRHa-treated women, P4 secretion was more than 50% less than in CCs of CG-treated women (P < 0.005). Addition of 20 alpha-hydroxycholesterol significantly increased P4 secretion in CCs collected from GnRHa-treated women, similar to P4 secretion in CCs collected from CG-treated women. This study evaluated for the first time the effectiveness of GnRHa administration on COC maturation. It seems that although oocyte meiotic maturation in GnRHa-treated women proceeds as in CG-stimulated women, CC steroidogenic activity is marked by cholesterol deficiency or availability.