17ñ-Hydroxypregnenolone is a pregnane (C21) steroid that is obtained by hydroxylation of pregnenolone at the C17ñ position. This step is performed by the mitochondrial cytochrome P450 enzyme 17ñ-hydroxylase (CYP17A1) that is present in the adrenal and gonads. Peak levels are reached in humans at the end of puberty and then decline. High levels are also achieved during pregnancy. It is also a known neuromodulator.
17ñ-Hydroxypregnenolone is considered a prohormone in the formation of dehydroepiandrosterone (DHEA), itself a prohormone of the sex steroids.
This conversion is mediated by the enzyme 17,20 lyase. As such 17ñ-hydroxypregnenolone represents an intermediary in the ÃÂ<sup>5</sup> pathway that leads from pregnenolone to DHEA. 17ñ-Hydroxypregnenolone is also converted to 17ñ-hydroxyprogesterone, a prohormone for glucocorticosteroids and androstenedione through the activity of 3ñ-hydroxysteroid dehydrogenase.
Measurements of 17ñ-hydroxypregnenolone are useful in the diagnosis of certain forms of congenital adrenal hyperplasia. In patients with congenital adrenal hyperplasia due to 3ò-hydroxysteroid dehydrogenase deficiency 17ñ-hydroxypregnenolone is increased, while in patients with congenital adrenal hyperplasia due to 17ñ-hydroxylase deficiency levels are low to absent.
17ñ-hydroxypregnenolone is a known neuromodulator as its acts in the central nervous system. Specifically, it is known to modulate locomotion.