ki-values for estradiol-17 beta , ( 0.8 microm ) , progesterone ( 27.0 microm ) and 20 alpha-dihydroprogesterone ( 1.5 microm ) were comparable to reported tissue levels of these compounds , consistent with a possible competition in vivo among naturally occurring c18- , c19- , and c21-steroids for the active site of microsomal 17 beta-hsd .
C0033308
progesterone
C0012311
20