Histrelin is a synthetic nonapeptide analog of gonadotropin-releasing hormone, consisting of pyroglutamyl, histidyl, tryptophyl, seryl, tyrosyl, 1-benzyl-D-histidyl, leucyl, arginyl, and N-ethylprolinamide residues. It is used as a subcutaneous hydrogel implant, particularly as the diacetate salt, for treating prostate cancer and suppressing gonadal sex hormone production in children with central precocious puberty. It functions as an antineoplastic agent and a gonadotropin-releasing hormone agonist.