Treatment method

A method for inhibiting ovarian steroidogenesis in women comprising administering to normal women with regular menstrual cycles an ovarian steroidogenesis inhibitorally effective amount of at least one peptide of the formula

• p Glu-His-Trp-Ser-Tyr-X-Y-Arg-Pro-Z
• wherein (a) Z is Gly-NH.sub.2, Y is Leu and X is Gly, (b) Z is Gly-NH.sub.2, Y is Leu, X is DN Leu, DN Val, D Abu (.alpha.-aminobutyric acid), D Phe, D Ser, D Thr, D Met, D Pgl, D Lys, Leu, Ile, Nle, Val, N-Val, Met, Phe, D Leu, D Arg, D ser (tbu), D Thr (tbu), D Cys (tbu), D Asp (O tbu), D Glu (Otbu), D Orn (boc), D Lys (boc), D Trp, Trp, 2-methyl Ala, D Tyr, D Met, .epsilon.-lauryl D Lys, .epsilon.-dextran-D Lys, (c) Z is NH-cyclopropyl- or NH-Alk wherein Alk is alkyl of 1 to 3 carbon atoms, Y is Leu and X is D Ser (tbu), D Thr (tbu), D Asp (Otbu), D Glu (Otbu), D Orn (boc), D Lys (boc), (d) Z is --NH--CH.sub.3, --NH--CH.sub.2 --CH.sub.3,--NH--CH.sub.2 --CH.sub.2 --CH.sub.3, --NH--C.H.sub.2 --CH.sub.2 --OH, ##STR2## Y is Leu and X is Gly, (e) Z is --NH--CH.sub.2 --CH.sub.3, Y is Leu and X is D Trp, D Leu, D Ala, D Ser (tbu), D Tyr, D Lys, Ala, (f) Z is Gly-NH.sub.2 or --NH--CH.sub.2 --CH.sub.3, Y is N.alpha.Met Leu and X is Gly (g) Z is --NH-cyclopropyl, Y is Leu and X is D Leu or (h) Z is Gly-NH.sub.2, --NH-cyclopropyl or --NHAlk' where Alk' is alkyl of 1 to 3 carbon atoms, Y is Ser (but), Cys (but), Asp (Obut), Glu (Obut), --Orn (boc), Lys (boc) and X is Gly.