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17-Hydroxypregnenolone (also 17-OH-pregnenolone and 17α-hydroxypregnenolone), is a C21 steroid that is obtained by hydroxylation of pregnenolone at the C17α position. This step is performed by the mitochondrial cytochrome P450 enzyme 17α-hydroxylase (CYP17A1) that is present in the adrenal and gonads. Peak levels are reached in humans at the end of puberty and then decline.^[1] High levels are also achieved during pregnancy.

ProhormoneEdit

17-OH-pregnenolone is considered a prohormone in the formation of dehydroepiandrosterone (DHEA), itself a prohomone of the sex steroids.

This conversion is mediated by the enzyme 17,20 lyase . As such 17-OH-pregenolone represents an intermediary in the delta-5-pathway that leads from pregnenolone to DHEA. 17-hydroxypregneolone is also converted to 17-hydroxyprogesterone, a prohomone for glucocorticosteroids and androstenedione through the activity of 3-hydroxysteroid dehydrogenase.

NeurohormoneEdit

There is some evidence that 17-OH-pregnenolone may have activity as a neurohormone.^[2]

Clinical useEdit

Measurements of 17-OH-pregnenolone are useful in the diagnosis of certain forms of congenital adrenal hyperplasia.^[3] In patients with congenital adrenal hyperplasia due to 3 beta-hydroxysteroid dehydrogenase deficiency 17-OH-pregnenolone is increased, while in patients with congenital adrenal hyperplasia due to 17 alpha-hydroxylase deficiency levels are low to absent.

See alsoEdit

Congenital adrenal hyperplasia

Additional imagesEdit

Steroidogenesis

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ReferencesEdit

1. ↑ Hill M, Lukac D, Lapcik O, Sulcova J, Hampl R, Pouzar V, Starka L. Age relationships and sex differences in serum levels of pregnenolone and 17-hydroxypregnenolone in healthy subjects. Clin Chem Lab Med. 1999 Apr;37(4):439-47. PMID 10369116
2. ↑ Matsunaga M, Ukena K, Baulieu EE, Tsutsui K 7alpha-Hydroxypregnenolone acts as a neuronal activator to stimulate locomotor activity of breeding newts by means of the dopaminergic system. Proc Natl Acad Sci USA 2004 Dec 7;101(49):17282-7. PMID 15569930
3. ↑ Riepe FG, Mahler P, Sippell, Partsch CJ. Longitudinal Study of Plasma Pregnenolone and 17-Hydroxypregnenolone in Full-Term and Preterm Neonates at Birth and during the Early Neonatal Period. The Journal of Clinical Endocrinology & Metabolism (2002) 87: 4301-4306 [1]

External linksEdit