Antagonist Protocol

Definition - What does Antagonist Protocol mean?

An antagonist protocol is a process used during in vitro fertilization (IVF) to prevent premature ovulation. It uses gonadotropin-releasing hormone (GnRH) antagonist medications such as Cetrotide and Ganirelix to stop the release of luteinizing hormone (LH) and follicle-stimulating hormone (FSH). Both are important hormones that direct the menstrual cycle and ovulation. GnRH antagonists quickly block the receptor (the place that receives signals from the body) that tells the body to release LH and FSH.

By "turning off" the body's natural hormones, they are less likely to interfere with IVF medications. The IVF medications take over by directing egg maturation, egg release, and preparing the uterine lining for embryo implantation.

FertilitySmarts explains Antagonist Protocol

The most common protocol used during IVF is the agonist protocol which uses GnRH agonists to slowly "down-regulate" the release of LH and FSH. The antagonist protocol has an advantage of stopping the release of LH and FSH faster with fewer days of medication. The antagonist protocol is a newer method with similar pregnancy rates compared to the agonist method. Often in cases of women who are at risk for ovarian hyperstimulation syndrome (OHSS) or those who have polycystic ovarian syndrome (PCOS), the antagonist protocol is preferred because fewer stimulation medications are needed to stimulate egg maturation. Stimulation medications often worsen these conditions with more hormonal exposure.

During the antagonist protocol, GnRH antagonists are given in combination with FSH stimulating medications on day 6 of FSH administration. FSH is important in promoting egg maturation and eventual egg release. GnRH anatagonists are given for a few days until ovulation is induced by an injection of human chorionic gonadotropin (hCG), also known as a trigger shot. About 48 hours after ovulation, the eggs are retrieved and fertilized and eventually returned to the uterus. Progesterone is often supplemented after ovulation to promote a healthy uterine lining for embryo implantation and continued until a pregnancy test.

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