Classical pathway of sex steroid synthesis and metabolism: DHEA and its sulfate (DHEAS), androstenedione, and estrone. Androstenedione is metabolized peripherally to testosterone and dihydrotestosterone, whereas estrone is metabolized to estradiol.
Definitions (enzyme activities): CYP11A1: cholesterol side-chain cleavage enzyme P450scc (20-hydroxylase, 22-hydroxylase, and 20,22-lyase) StAR: steroidogenic acute regulatory protein CYP17A1: P450c17 (17-alpha-hydroxylase and 17,20-lyase) POR: P450 oxidoreductase HSD17B5: 17-beta-hydroxysteroid dehydrogenase type 5 (17-ketoreductase) HSD3B2: 3-beta-hydroxysteroid dehydrogenase type 2 HSD3B1: 3-beta-hydroxysteroid dehydrogenase type 1 CYP21A2: P450c21 (21-hydroxylase) CYP11B1: P450c11 (11-beta-hydroxylase) CYP11B2: aldosterone synthase (18-hydroxylase [corticosterone methyloxidase I] and 18-dehydrogenase [corticosterone methyloxidase II]) HSD11B2: 11-beta-hydroxysteroid dehydrogenase type 2