The main effects produced by the use of analogs that are GnRH agonists are, on the one hand, the initial release of gonadotropins (flare-up effect) and then blocking the release of these gonadotropins, preventing the communication between the pituitary gland and the ovary so that there is no follicular development or ovulation.
All this occurs temporarily when the reserve of FSH and LH in the pituitary is empty. Normally, the total blockage of GnRH receptors occurs between 5-10 days after the first administration of the agonist.