Zona fasciculata, steroid synthesis

Adrenal steroid synthesis. The adrenal cortex consists of three histologically distinct zones the zona glomerulosa, zona fasciculata, and an innermost layer called the zona reticularis. Each zone is responsible for production of different hormones. (17 =... 

Diagrammatic representation of zone-specific steroid synthesis in the adrenal cortex. All three zones can convert cholesterol into pregnenolone, but because of the presence/absence of certain enzymes, the flow of pregnenolone is preferentially directed to the synthesis of the steroid for which the particular zone is specific. It has not been determined whether the zona fasciculata produces dehydroepiandrosterone (DHEA) and dehydroepiandrosterone sulphate (DHEAS) in physiologically significant amounts. 

Biosynthesis of adrenai corticosteroids. The primary precursor is acetyl-CoA and biosynthesis proceeds via cholesterol (see Terpenes, Steroids). The adrenal cortex also utilizes cholesterol which it receives as cholesterol esters from extra- adrenal sources (see Lipoproteins). The adrenal cortex is differentiated into 3 concentric layers. The outermost layer (zona glomerulosa) is primarily responsible for synthesis and secretion of aldosterone It contains the 18-hydroxylase and lacks the 17a-hydroxylase. The intermediate layer (zona fasciculata) and innermost layer (zona reticularis) are responsible for the synthesis of glucocorticoids (mainly cortisol) and adrenal androgens they possess the 17a-hydroxy-lase and lack the 18-hydroxylase. 

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