the affinities of steroids for the progesterone receptor were as follows : norethindrone ( ki of 2.3 x 10 ( -9 ) m ) greater than 5alpha-dihydronorethindrone greater than norethindrone acetate greater than lynestrenol greater than 17alpha-ethynyl-estra-4-ene-3beta , 17beta-diol greater than ethynodiol diacetate ( ki of 1.3 x 10 ( -7 ) m ) .
C0028356
norethindrone
C0068980
norethindrone acetate