Histrelin is a synthetic gonadotropin-releasing hormone (GNRH) agonist that binds to the GNRH receptor (GNRHR; Ki = 0.2 nM in CHO cells expressing the human receptor). It stimulates release of oxytocin and vasopressin ex vivo from the isolated rat hypothalamo-neurohypophysial system at a concentration of 100 nM. In vivo, the initial dose of histrelin (100 μg) stimulates acute increases in luteinizing hormone (LH), follicle-stimulating hormone (FSH), and testosterone serum levels (50-, 2.5-, and 15-fold, respectively), while chronic treatment leads to 95% decreases in LH and FSH responses in rhesus monkeys. Formulations containing histrelin have been used in the treatment of advanced prostate cancer and central precocious puberty.