Abstract
Bio-assay by the Hooker-Forbes method of mixtures of progesterone, 20α-hydroxy-4-pregnen-3-one, 20β-hydroxy-4-pregnen-3-one, 16α-hydroxyprogesterone and 17α-hydroxyprogesterone revealed synergisms, partial antagonisms and complete antagonisms, depending upon the components and their proportions in the mixtures. (Endocrinology75: 799, 1964)