the 5 alpha-reductase for testosterone was competitively inhibited by delta 4-3-oxosteroids such as progesterone , 20 alpha-dihydroprogesterone , 17 alpha-hydroxyprogesterone , 4-androstenedione , 11-deoxycorticosterone , corticosterone and 11-deoxycortisol , which had inhibition constants ( ki ) of 3.3 x 10 ( -9 ) m , 2.2 x 10 ( -9 ) m , 1.8 x 10 ( -8 ) m , 1.3 x 10 ( -8 ) m , 8.3 x 10 ( -9 ) m , 1.5 x 10 ( -7 ) m and 8.7 x 10 ( -8 ) m , respectively , suggesting the possibility that the 5 alpha-reduction of testosterone is regulated by other delta 4-3-oxosteroids .
C0033308
progesterone
C0012311
20 alpha-dihydroprogesterone