experiments were therefore carried out to study the transfer of three pairs of steroids ( progesterone and 20 alpha-dihydroprogesterone , c-21 ; androstenedione and testosterone , c-19 ; and estrone and estradiol-17 beta , c-18 ) in which each member of a pair differed by one hydroxyl group .
C0033308
progesterone
C0012311
20 alpha-dihydroprogesterone