1. Harvard Center for Reproductive Endocrine Sciences (C.M., R.B., A.A.D., M.G.A., Y.S., U.B.K., S.B.S., N.P., W.F.C.), Department of Medicine, Massachusetts General Hospital, Boston, Massachusetts 02114;
2. Reproductive Endocrine Unit (C.M., R.B., A.A.D., M.G.A., Y.S., S.B.S., N.P., W.F.C.), Department of Medicine, Massachusetts General Hospital, Boston, Massachusetts 02114;
3. Brigham and Women's Hospital and Harvard Medical School (U.B.K.), Boston, Massachusetts 02115;
4. Department of Pharmacology (Q.-Y.Z.), University of California, Irvine, California 92697