(Des-Gly10, D-Ala6, Pro-NHEt9) -LHRH (Surfagon, Mwt 1167.34 Da) is an agonist of gonadotropin-releasing hormone (GnRH) . (Des-Gly10, D-Ala6, Pro-NHEt9) -LHRH can be used as an internal standard for the LC-MS analysis of leuprorelide acetate. (Des-Gly10, D-Ala6, Pro-NHEt9) -LHRH has potential applications in biochemical analysis and fertility[1][2][3].