January 3, 2008
Interesting – if GnRH antagonist can block cellular division and decrease the secretion of E2 from the ovaries, could this be a part of the mechanism of increasing the follicular phase in the preceding article? Often we only think drugs have a singular effect, GnRH antagonist should only effect pituitary, yet GnRH receptors exist in the ovaries/follicles and play an important role in embryonic growth. If GnRH has a role in cellular replacement/growth, then could some problems with embryonic quality be related to drugs blocking important hormonal receptors?
From a Chinese perspective GnRH would be considered a qi mover. Qi movers help to keep energy flowing and transforming. An example would be electricity coming through the outlet and into the plug. It flows without any resistance and moves into the appliance. Once the electricity enters into the appliance, it is transformed into an action, such as light, heat, cool air or a picture. When one part of the action fails, it effects the other. In a trying to conceive, emotional stress can constrict/block qi causing menstrual irregularities, intense PMS and a lack of libido. If a basic hormone (GnRH) plays an important role in moving qi, could acupuncture/Chinese herbs improve the body’s ability to utilize it correctly resulting in pregnancy? Maybe future research will investigate.
Early cleavage does not predict treatment outcome following the use of GnRH antagonists in women older than 35
Embryo selection is traditionally performed by using embryo morphology as the guideline. Other selection methods include oocyte and pronuclei polarity and morphology, blastomere symmetry, and blastocyst culture. Several studies have shown that early embryonic cleavage, which is the time period 25–27 hours postinsemination/intracytoplasmic sperm injection (ICSI), can be a strong indicator of viable embryos.
Previous studies have shown that GnRH antagonists are associated with a lower usage of gonadotropins, a shorter duration of stimulation, and a lower cycle cancellation rate, especially in poor responders. Some animal studies have shown that GnRH receptor mRNA is present in developing embryos, and that preimplantation embryonic development is significantly decreased by GnRH antagonists in vitro. In this study we collected data from patients who were older than 35 years undergoing assisted reproduction treatment to investigate the clinical effect of GnRH antagonists. The primary purpose of this study was to compare rates of oocyte maturation and early embryonic development (especially the early cleavage of embryos) between patients administered GnRH antagonists and those administered GnRH agonists during a long protocol. Furthermore, implantation and pregnancy rates were also compared.
A total of 220 embryo transfer cycles were included in this study; 68 patients were treated with antagonists and the other 152 patients with agonists.
Ovarian Stimulation Protocol
Two stimulation protocols were used in this study.
1) the GnRH antagonist protocol (GnRH antagonist group).
a. In the GnRH antagonist group, recombinant FSH (Gonal-F) and hMG (Pergonal) were administrated daily from the second day of the menstrual cycle. Cetrorelix (Cetrotide) was administered subcutaneously at a dose of 0.25 mg daily when the dominant follicle reached 14 mm in mean diameter, until the day of hCG administration.
2) the long protocol for GnRH agonists (GnRH agonist group).
a. In the long GnRH agonist group, leuprolide acetate was given at a daily dose of 1 mg, starting on day 21 of the previous cycle. Once serum levels of E2 <30 pg/mL were achieved, the daily dose of leuprolide acetate was reduced to 0.5 mg and recombinant FSH and hMG were given until the day of hCG administration.
In each stimulation protocol, patients who had at least one early-cleavage embryo transferred were designated as the “early-cleavage subgroup.” Patients who had no early-cleavage embryos transferred were designated as the “late-cleavage subgroup.”
Implantation was defined by the observation of a gestational sac in the uterus by transvaginal ultrasonography. An ongoing pregnancy was defined by the observation of a fetal heartbeat on ultrasonography after 12 weeks of gestation. Abortion was defined as fetal loss before 12 weeks of gestation.
Assessment of Early Cleavage and Embryo Quality
Embryos displaying two cells at inspection were designated as “early cleavage,” whereas those embryos that had not yet cleaved to the two-cell stage were designated as “late cleavage.” Embryos were further examined for their quality at 44–46 hours (day 2) and 66–68 hours (day 3).
In this study, a total of 1,163 normally fertilized oocytes were derived, including 340 zygotes from the antagonist group and 823 zygotes from the agonist group. Thirty of 68 (44.1%) patients receiving GnRH antagonists had at least one early-cleavage embryo following treatment, while 105 of 152 (69.1%) patients with GnRH agonists had at least one early-cleavage embryo. The percentage of patients with “early-cleavage” embryos was significantly higher in the GnRH agonist group compared with the GnRH antagonist group.
*Patients who had at least one early-cleavage embryo transferred were designated as the “early-cleavage subgroup.”
*Patients who had no early-cleavage embryos transferred were designated as the “late-cleavage subgroup.”
*In the antagonist group, 30 of 68 patients had at least one early-cleavage embryo transferred while 38 patients had only late-cleavage embryos transferred.
*In the antagonist group, a total of 30 patients conceived successfully. Twelve of 30 (40%) women conceived in the early-cleavage subgroup.
*In the antagonist group 18 of 38 (47.4%) women conceived in the late-cleavage subgroup. Although the pregnancy rate appears higher in the late-cleavage subgroup (40.0% vs. 47%), though the difference was not statistically significant.
*In the GnRH agonist group, 105 patients had at least one early-cleavage embryo transferred (early-cleavage subgroup) while 47 patients had only late-cleavage embryos transferred (late-cleavage subgroup).
*In the GnRH agonist group, a total of 78 patients conceived. Sixty-four of 105 (61.0%) women conceived in the early-cleavage subgroup, while 14 of 47 (29.8%) women conceived in the late-cleavage subgroup. The pregnancy rate was significantly higher in the early-cleavage subgroup than in the late-cleavage subgroup (61.0% vs. 29.8%).
Ongoing pregnancy rates were all similar between the antagonist and agonist groups. Furthermore, early-cleavage was not a reliable predictor of pregnancy in patients over 35 years old stimulated with GnRH antagonist protocols.
In the antagonist group, there was no difference in the pregnancy rates between the early-cleavage subgroup and late-cleavage subgroup (40.0% vs. 47.4%). Therefore, early cleavage is not a good predictor of pregnancy outcome in patients over 35 years old stimulated with GnRH antagonist protocols. The exact mechanism underlying early cleavage in human embryogenesis is still unclear. Studies have shown that GnRH antagonist administration was able to block early embryonic development. Is it possible that high doses of GnRH antagonists affect mitotic gene expression? GnRH antagonists act through competitive binding to GnRH receptors, a situation that can be reversed by GnRH. Previous studies have shown that continuous exposure to GnRH antagonists will induce down-regulation of the GnRH receptor and a decrease in GnRH receptor gene expression. In these in vitro studies, GnRH antagonists restricted cell growth and restricts receptors that form the basis for the generation of an important mitogenic cascade.
If cellular growth pathways are inhibited by GnRH antagonists, early cleavage could be retarded. The presence of the GnRH receptors in the developing embryo and preimplantation embryonic development were significantly decreased by GnRH antagonists. This detrimental effect of the GnRH antagonist on preimplantation embryonic development was a specific receptor-mediated effect, rather than a toxic effect. In IVF cycles, the GnRH antagonist is suspended when hCG is applied, and the embryo is transferred between 5 and 7 days after the last dose of GnRH antagonist. The half-life of the GnRH antagonist reported is 30 hours, and the time interval between the last dose of the GnRH antagonist to the early cleavage of zygotes is about 80 to 90 hours. Consequently, the GnRH antagonist may still have some effect on zygotes to delay the first mitosis. This could explain why lower rates of early cleavage were found in women stimulated with GnRH antagonist protocols. In the following 20 to 40 hours, the potential detrimental effect on the developing embryo may be significantly diminished. This could be the reason for a lack of effect of the GnRH antagonist on pregnancy outcome. We believe that by using a GnRH antagonist protocol for ovarian stimulation, there is a delay in the first mitosis of the zygote but later embryonic development is not affected because of the short half-life of the GnRH antagonist.
The use of GnRH antagonist therapy in women undergoing assisted reproduction has a significant effect on ovarian follicular steroidogenesis, as demonstrated in several studies. In the present study, the E2 level on the day of hCG administration was significantly lower in the GnRH antagonist group. It has been reported reduced aromatase activity in granulosa lutein cells from patients treated with GnRH antagonists. The reduced aromatase activity might explain the lower E2 concentrations. As mentioned above, GnRH receptors are found in the ovaries, especially in granulosa-lutein cells. If GnRH antagonists inhibit the synthesis of growth factors involved in the cell cycle of granulosa cells, the rate of apoptosis (cellular death) within them will be accelerated, in turn affecting follicular steroidogenesis.
Interestingly, in the present study, although the E2 level on the day of hCG administration was significantly lower in the GnRH antagonist group, the number of retrieved oocytes, and oocyte maturation and fertilization rates were similar in comparison with the GnRH agonist group. Furthermore, the implantation and pregnancy rates showed no statistically significant difference between the two groups. Previous studies have shown a lack of evidence supporting any association between the serum E2 level on the day of hCG administration and the clinical pregnancy rate. The finding of similar oocyte maturation and fertilization rates accompanied with lower serum E2 levels on the day of hCG administration when using GnRH antagonists was also observed in other studies. It has been suggested that the serum E2 level may act as a marker of oocyte maturation rather than as a factor controlling maturation. Therefore, this suggests a possible direct role of GnRH antagonists on E2 production within the ovary, without other effects upon follicular development.