Mechanism GnRH analog See female hypothalamic-pituitary axis topic See male hypothalamic-pituitary axis topic Action depends on mode of administration GnRH antagonist when infusion continuously causes initial increase in androgens after initial administration GnRH agonist when infused in a pulsatile manner is the natural way the body releases GnRH Indications Infertility (pulsatile) Prostate cancer (continuous) coadministered with flutamide Uterine fibroids Toxicity Antiandrogen side effects Nausea Vomiting