• 17α-Hydroxypregnenolone is a pregnane (C21) steroid that is obtained by hydroxylation of pregnenolone at the C17α position. This step is performed by the mitochondrialcytochrome 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.
  • ^{Hill M, Lukác D, Lapcík O, Sulcová J, Hampl R, Pouzar V, Stárka L (April 1999). “Age relationships and sex differences in serum levels of pregnenolone and 17-hydroxypregnenolone in healthy subjects”. Clinical Chemistry and Laboratory Medicine. 37 (4): 439–47. doi:10.1515/CCLM.1999.072. PMID 10369116} 
• High levels are also achieved during pregnancy.
• It is also a known neuromodulator.

Prohormone

• 17α-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 17α-hydroxypregenolone represents an intermediary in the Δ⁵ pathway that leads from pregnenolone to DHEA. 17α-Hydroxypregneolone is also converted to 17α-hydroxyprogesterone, a prohormone for glucocorticosteroids and androstenedione through the activity of 3α-hydroxysteroid dehydrogenase.

Clinical use

• Measurements of 17α-hydroxypregnenolone are useful in the diagnosis of certain forms of congenital adrenal hyperplasia.
  • ^{Riepe FG, Mahler P, Sippell WG, Partsch CJ (September 2002). “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 and Metabolism. 87 (9): 4301–6. doi:10.1210/jc.2002-020452. PMID 12213889} 
• In patients with congenital adrenal hyperplasia due to 3β-hydroxysteroid dehydrogenase deficiency 17α-hydroxypregnenolone is increased, while in patients with congenital adrenal hyperplasia due to 17α-hydroxylase deficiency levels are low to absent.

Neurosteroid

• 17α-hydroxypregnenolone is a known neuromodulator as its acts in the central nervous system. Specifically, it is known to modulate locomotion.
  • ^{Tsutsui K, Haraguchi S, Vaudry H (September 2018). “7α-Hydroxypregnenolone regulating locomotor behavior identified in the brain and pineal gland across vertebrates”. General and Comparative Endocrinology. 265: 97–105. doi:10.1016/j.ygcen.2017.09.014. PMID 28919448.}

See also

• Congenital adrenal hyperplasia