GnRH agonists act as agonists of the GnRH receptor, the biological target of gonadotropin-releasing hormone (GnRH). These drugs can be both peptides and small-molecules. They are modeled after the hypothalamic neurohormone GnRH, which interacts with the GnRH receptor to elicit its biologic response, the release of the pituitary hormones follicle-stimulating hormone (FSH) and luteinizing hormone (LH). However, after the initial "flare" response, continued stimulation with GnRH agonists desensitizes the pituitary gland (by causing GnRH receptor downregulation) to GnRH. Pituitary desensitization reduces the secretion of LH and FSH and thus induces a state of hypogonadotropic hypogonadal anovulation, sometimes referred to as “pseudomenopause” or “medical oophorectomy.” GnRH agonists are able to completely shutdown gonadal testosterone production and thereby suppress circulating testosterone levels by 95% or into the castrate/female range in men.