Journal of Endocrinology

Steroidogenesis in the adrenal cortex. Shown are the pathways by which the adrenal cortex synthesizes aldosterone in the zona glomerulosa, cortisol in the zona fasciculata and dehydroepiandrosterone (DHEA) and DHEA sulfate (DHEA-S) in the zona reticularis. All steroid hormones are synthesized from cholesterol, which is transported by the protein steroidogenic acute regulatory (StAR) protein from the outer to the inner mitochondrial membrane, where the initial step of side-chain cleavage is catalyzed by CYP11A1 to yield pregnenolone. CYP17 is an enzyme with two activities, hydroxylation and lyase, which allows the synthesis of cortisol and DHEA. CYP11B2 is expressed in the zona glomerulosa where the protein encoded by this gene, aldosterone synthase, is required for aldosterone production, catalyzing the last three reactions in aldosterone biosynthesis, 11-hydroxylation followed by 18-hydroxylation and subsequent oxidation to yield an aldehyde. CYP11B1, on the other hand, produces cortisol in the zona fasciculata.