GnRH agonists (e.g. Gonapeptyl, Decapeptyl, Diphereline) are used in complementary treatment in combination with the administration of gonadotropins, during the preparation for in vitro fertilization. Administered in the form of injection, they can be used as a short-acting medication (given every day) or as a long-acting drug used during the preparation which lasts for 1 to 3 months (e.g. in patients with endometriosis). The administration of the preparation in the first phase stimulates the pituitary secretion of LH and FSH and in consequence raises the threshold of pituitary sensitivity and decreases the secretion of gonadotropins. As a result, blood sex hormone level is decreased to the values present after the period of expiration of gonad activity. These effects are transient. The basic role of the medication is to prevent the premature LH surge which could cause the release of egg cells before they reach sufficient maturity. GnRH agonists belong to the class of drugs which are intended to prevent premature ovulation.
These medications, by causing the secretion of FSH and LH from the pituitary gland, can be used in order to start the growth of follicles and the last stages of egg cell maturation.