P450 C_17-20 (17α-hydroxylase)

17α-hydroxylase (P450c _17-20) catalyzes hydroxylation and cleavage of steroids (converts steroids from a 21-carbon to a 19-carbon molecule in Δ4 and Δ5- hydroxysteroid pathways);

Production/Activity Regulated by:

-   LH

P450c₁₇ Activity suppressed by:

-   TESTOSTERONE (via effects on second messenger cAMP pathway)

17α-hydroxylase /C17-20 lyasepathway directly affected by:

-   Nicotine;

-   Ethanol (17α-hydroxylase)

-   Drugs: Bromocriptine, Mibolerone, Danazol, Cyproterone acetate, Cyclosporin A, Flutamide.

•In rats, P450 C₁₇ catalyses:

17α-HydroxyPROGESTERONE ➔  ANDROSTENEDIONE

(but not in humans, which could explain differences between rat and human studies);