17-Hydroxypregnenolone (also 17-OH-pregnenolone and 17 -hydroxypregnenolone), is a C21 steroid that is obtained by hydroxylation of pregnenolone at the C17 position. This step is performed by the mitochondrial cytochrome P450 enzyme 17 -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.

Prohormone

17 OH pregnenolone is converted from pregnenolone and gives rise to DHEA (below) and to 17 OH-progesterone (to its right)

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 prohormone for glucocorticosteroids and androstenedione through the activity of 3-hydroxysteroid dehydrogenase.

Neurohormone

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

Clinical use

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 also

Congenital adrenal hyperplasia

Additional images

<gallery> File:Steroidogenesis.svg|Steroidogenesis </gallery>

References

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