The amino acids at positions 1, 2, 3, 6, 8 and 10 of the natural GnRH decapeptide have been substituted resulting in N-Ac-D-Nal(2)1, D- -pClPhe2, D-Pal(3)3, D-hArg(Et2)6, L-hArg(Et2)8, D-Ala10]-GnRH with a molecular weight of 1570.4.