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Pregnenolone
3β-hydroxypregn-5-en-20-one IUPAC name
CAS number 145-13-1	ATC code [[ATC_code_|]][1]
PubChem 8955	DrugBank EXPT02608
Chemical formula	{{{chemical_formula}}}
Molecular weight	316.483 g/mol
Bioavailability
Metabolism
Elimination half-life
Excretion
Pregnancy category
Legal status
Routes of administration

Pregnenolone is a steroid hormone involved in the steroidogenesis of progesterone, mineralocorticoids, glucocorticoids, androgens, and estrogens. As such it is a prohormone.

Contents 1 Chemistry 2 Synthesis 3 Prohormone 4 Neurosteroid 5 Additional images 6 References

[edit] Chemistry

Like other steroids, pregnenolone consists of four interconnected cyclic hydrocarbons. It contains ketone and hydroxyl functional groups, two methyl branches, and a double bond at C5, in the B cyclic hydrocarbon ring. Like all steroid hormones, it is hydrophobic. Its esterified version, pregnenolone sulfate, is water soluble.

[edit] Synthesis

Pregnenolone is synthesized from cholesterol. This conversion involves hydroxylation at the side chain at C20 and C22 positions, with cleavage of the side chain. The enzyme performing this task is cytochrome P450scc, located in the mitochondria, and controlled by pituitary tropic hormones, such as ACTH, FSH, LH.

[edit] Prohormone

Pregnenolone undergoes further steroid metabolism in one of two ways.

• Pregnenolone can be converted to progesterone. The critical enzyme step is two-fold using a 3-beta-hydroxysteroid dehydrogenase and a delta 4-5 isomerase. The latter transfers the double bond from C5 to C4 on the A ring. Progesterone is the entry into the delta-4-pathway resulting in production of 17-hydroxy progesterone, and androstenedione, precursor to testosterone and estrone. Aldosterone and corticosteroids are also derived from progesterone or its derivatives.

• Pregnenolone can be converted to 17-hydroxy-pregnenolone by the enzyme 17α-hydroxylase (CYP17A1). Using this pathway, termed delta-5 pathway, the next step is conversion to dehydroepiandrosterone (DHEA) using a desmolase. DHEA is the precursor of androstenedione.

[edit] Neurosteroid

Pregnenolone and its sulfate, like dehydroepiandrosterone and its sulfate and progesterone, belong to the group of neurosteroids that are found in high concentrations in certain areas in the brain and are synthesized there. Neurosteroids affect synaptic functioning, are neuroprotective, and enhance myelinization. Pregnenolone and its sulfate ester are under investigation for their potential to improve cognitive and memory functioning.^[1]

[edit] Additional images

Steroidogenesis

Cholesterol

Progesterone

[edit] References

1. ↑ Vallée M, Mayo W, Le Moal M (2001). Role of pregnenolone, dehydroepiandrosterone and their sulfate esters on learning and memory in cognitive aging.. Brain Res Brain Res Rev 37 (1-3): 301-12. PMID 11744095.

Template:Biochemical families

General:
Precursors:	Squalene | Lanosterol
Common:	Cholesterol | Pregnenolone | 17-Hydroxypregnenolone | DHEA | Androstenedione | Androstanediol
Estrogens:	Estradiol | Estriol | Estrone
Androgens:	Testosterone | Dihydrotestosterone | Androsterone
Progestagens:	Progesterone | 17-Hydroxyprogesterone | Progestins
Glucocorticoids:	Cortisol | Prednisone
Mineralocorticoids:	Aldosterone
Phytosterols:	Stigmasterol | Brassicasterol
Ergosterols:	Ergosterol | Ergocalciferol