Box 4.5Synthesis of the major steroid hormones secreted by the adrenal cortex

Image ch4fb5.jpg

Image dclcc1.jpg The genes coding for the P450 enzymes are abbreviated to CYP and the first step in the synthesis of hormones is the 6 carbon unit side chain cleavage of cholesterol. Many of the subsequent steps also require P450 enzymes which activate oxygen and induce hydroxylations.

Image dclcc2.jpg Conversion of pregnenolone to progesterone requires oxidation of the 3-OH group and isomerization of the Δ5 double bond to Δ4 by 3β-hydroxysteroid-dehydrogenase (HSD).

Image dclcc3.jpg Synthesis of cortisol and androgens requires C-17 hydroxylations of pregnenolone or progesterone.

Image dclcc4.jpg Cortisol is formed by the subsequent hydroxylations at C-21 and C-11.

Image dclcc5.jpg DHEA (+ sulfated form) and androstenedione are formed by removal of the two-carbon side chain at C-17.

Image dclcc6.jpg Aldosterone is formed from progesterone by subsequent hydroxylations at C-21 and C-11 followed by oxidation of the C-18 methyl group (CH3) to an aldehyde (CH=O).

Synthesis of steroid requires trafficking between mitochondria and smooth endoplasmic reticulum. Shaded boxes indicate mitochondrial enzymes. All others are in the smooth endoplasmic reticulum.

From: Chapter 4, The adrenal gland

Cover of Endocrinology
Endocrinology: An Integrated Approach.
Nussey S, Whitehead S.
Copyright © 2001, BIOS Scientific Publishers Limited.

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