Metabolism of cortisol
Biosynthesis
Cortisol or D-4-pregnene-3-20-dione-11,17,21-triol results from cholesterol through pregnenolone and 17-a-hydroxyprogesterone. Its synthesis is carried out mainly in the fasciculata and reticularis parts of the adrenal cortex.
Some compounds: aminoglutethimide, metyrapone, ketoconazole, mitotane, inhibit the biosynthesis of cortisol and that of other steroids.
Plasma concentration
Plasma cortisol concentration follows circadian modifications parallel to those of ACTH: their concentrations increase from midnight to a maximum around six hours in the morning and decrease then gradually until midnight.
In plasma, cortisol is bound to a glycoprotein and to albumin. Its plasma half-life is approximately six hours. Cortisol, reduced form, is in equilibrium with its oxidized form, cortisone.
Catabolism
Its catabolism is primarily hepatic and includes reactions of reduction of the 4-5 double bond and of the 3-ketone and oxidation of OH groups in position 11 and 17 as well as conjugations.
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