GnRH antagonists are used in assisted reproductive treatments such as conventional in vitro fertilisation or ICSI. This increases egg production within a single menstrual cycle, enhancing thus the chances for getting pregnant.
Its most remarkable effect is the blockage of GnRH receptors. GnRH antagonists bind to them, impeding this way that the GnRH hormone binds to the GnRH receptors (competitive blockage).
GnRH receptors are located on the surface of the pituitary gonadotrope cells. The pituitary gland or hypophysis is a gland placed at the base of the brain, whose main function is to segregate and regulate the levels of different hormones. Some of the hormones produced by the pituitary gland are involved in the women’s menstrual cycle.
Apart from blocking GnRH receptors in the pituitary gland, GnRH antagonists have further beneficial qualities. Thus, they are recommended in many cases. Some of these qualities are mentioned hereafter:
- It blocks the synthesis of gonadotropins (FSH and LH) by the hypophysis, since it blocks GnRH receptors.
- They have an immediate onset of action.
- It prevents the flare-up effect of GnRH agonists to occur.
The flare-up effect consists of a mass release of FSH hormone (follicle-stimulating hormone) and LH hormone (luteinizing hormone). This is counterproductive and may lead to complications because of too high levels of both hormones.