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tell me more about pregnenolone
Pregnenolone is a steroid hormone, in the family of compounds known as pregnanes (which also includes other important hormones such as progesterone and cortisol). Pregnenolone is produced by the zona reticularis layer of the adrenal cortex. Under ACTH stimulation, it can be synthesized from cholesterol.
In humans, pregnenolone is produced in the zona reticularis of the adrenal cortex. In animals, it is synthesized from cholesterol primarily by steroidogenic cells (also called luteinizing hormone/choriogonadotropic–LH-CG) of the anterior pituitary gland.
In humans, pregnenolone is the precursor of many steroidal hormones: DHEA, progesterone, testosterone and aldosterone. The conversion from pregnenolone to these other steroids involves enzymatic steps within mitochondria.
The role of pregnenolone in steroidogenesis is to serve as a substrate for the synthesis of more active steroids. Pregnenolone can be converted into progesterone, which serves primarily as precursor for estrogen and testosterone (see below)
Pregnenolone can be converted to progesterone. The conversion of pregnenolone into progesterone involves three enzymatic steps: the first is catalyzed by 3beta-hydroxysteroid dehydrogenase/delta(5)-delta(4)isomerase, which converts it into 5α-pregnanedione; then 5α-pregnanedione (which is also called Δ1-3β-hydroxy steroid delta 4), along with cholesterol, are acted upon by steroid Δ4(5)-Δ7 isomerase to form 7α,8α-epidihydroprogesteron (also called allopregnanolone); and finally, this compound reacts in a complex with another enzyme known as 17β–hydroxysteroid reductase type 1 in order to convert itself into progesterone.
Pregnenolone can be converted into testosterone. Steroidogenesis in the testes begins with 3β-hydroxysteroid dehydrogenase/Δ(5)-Δ(4) isomerase, which converts cholesterol into pregnenolone. Pregnenolone is then transformed by several enzymatic steps (including the conversion of some androstenedione into estrone) into the androgens testosterone progesterone (which serves as precursor for estrogen). This pathway produces an estimated 100 millimoles of testosterone per day.