pregnenolone

Pregnenolone is a naturally occurring steroid hormone and neurosteroid that serves as the primary precursor in the biosynthesis of all other steroid hormones. It is produced mainly in the mitochondria of steroidogenic tissues, especially the adrenal cortex and gonads, and to a lesser extent in the brain, from cholesterol via the cholesterol side-chain cleavage enzyme (CYP11A1).

From pregnenolone, downstream enzymes convert it to progesterone via 3β-hydroxysteroid dehydrogenase and to other steroid pathways, including the production of androgens and estrogens through further steps involving CYP17A1 and related enzymes. In the brain, pregnenolone and pregnenolone sulfate are considered neurosteroids, with roles in modulating neuronal excitability and synaptic function, and potential effects on mood, learning, and memory, though mechanisms are not fully understood.

Clinical use of pregnenolone as a drug is not approved by major regulatory agencies; it is sometimes marketed as a dietary supplement. Evidence for benefits in mood or cognitive function remains inconclusive, and long-term safety data are limited. Possible adverse effects include hormonal imbalance, acne, hair loss, and interactions with hormone-dependent conditions, underscoring the need for medical supervision when considering supplementation.