Multienzyme Complexes/genetics; Progesterone Reductase/genetics; Steroid Isomerases/genetics; Adrenal Glands/enzymology; Amino Acid Sequence; Animals; Base Sequence; Evolution, Molecular; Female; Gene Expression Regulation, Enzymologic; Gonads/enzymology; Humans; Isoenzymes; Male; Molecular Sequence Data; Multienzyme Complexes/chemistry; Multienzyme Complexes/deficiency; Multienzyme Complexes/metabolism; Organ Specificity; Phylogeny; Placenta/enzymology; Pregnancy; Progesterone Reductase/chemistry; Progesterone Reductase/deficiency; Progesterone Reductase/metabolism; Promoter Regions, Genetic/genetics; Species Specificity; Steroid Isomerases/chemistry; Steroid Isomerases/deficiency; Steroid Isomerases/metabolism; Structure-Activity Relationship