The Pregnenolone Steal Pathway describes a hypothetical or clinical scenario where excessive demand for cortisol production, often driven by chronic stress, diverts the common precursor pregnenolone away from the synthesis of downstream sex hormones like testosterone and progesterone. This diversion can result in functional deficiencies in anabolic or reproductive hormones despite adequate precursor availability. It highlights the prioritization of the HPA axis over gonadal function.
Origin
This concept is illustrative, borrowing from the historical understanding of steroidogenesis, where pregnenolone serves as the initial step from cholesterol. The term “steal” is metaphorical, emphasizing the competitive utilization of this intermediate substrate by the adrenal glands when under chronic stimulation, such as in persistent high ACTH states.
Mechanism
The mechanism hinges on the activity of the mitochondrial enzyme Cholesterol Side-Chain Cleavage enzyme (CYP11A1), which converts cholesterol to pregnenolone, and subsequent enzyme activity favoring cortisol synthesis pathways (e.g., 17-alpha-hydroxylase) over those leading to DHEA or progesterone. Chronically elevated demand for glucocorticoids effectively saturates the shared metabolic machinery, thereby limiting the substrate flux available for mineralocorticoid and androgen synthesis downstream.
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