The highest level of the cholesterol side-chain cleavage system is found in the adrenal cortex and the corpus luteum.

[9] Immunofluorescence studies using specific antibodies against P450scc system enzymes have demonstrated that proteins are located exclusively within the mitochondria.

The final step cleaves the bond between carbons 20 and 22, resulting in the production of pregnenolone and isocaproic aldehyde.

[5] In adrenal cortex cells from zona fasciculata, the expression of the mRNAs encoding all three P450scc proteins is induced by corticotropin (ACTH).

Upon stimulation of a cell to make steroid, the amount of StAR available to transfer cholesterol to the inner membrane limits how fast the reaction can go (the acute phase).

With prolonged (chronic) stimulation, it is thought that cholesterol supply becomes no longer an issue and that the capacity of the system to make steroid (i.e., level of P450scc in the mitochondria) is now more important.

A study of the steroidogenic capacity of the adrenal cortex in infants with acute respiratory disease demonstrated that indeed during disease state there is a specific increase in the steroidogenic capacity for the synthesis of the glucocorticoid cortisol but not for the mineralocorticoid aldosterone or androgen DHEAS that are secreted from other zones of the adrenal cortex.

[24] Mutations in the CYP11A1 gene result in a steroid hormone deficiency, causing a minority of cases of the rare and potentially fatal condition lipoid congenital adrenal hyperplasia.