25-Hydroxycholesterol is a derivative of cholesterol, which plays a role in various biological processes in humans and other species.

It is involved in cholesterol metabolism, antivirus process, inflammatory and immune response, and survival signaling pathway.

25-hydroxycholesterol is biosynthesized from cholesterol by adding a hydroxyl group at the position 25-carbon of a steroid nucleus.

[1][2] The CYP3A4 enzyme, a member of the cytochrome P450 family, can catalyze the oxidation of 25-hydroxycholesterol to 7α,25-dihydroxycholesterol, whereas 25-hydroxycholesterol can inhibit CYP4F2 mRNA expression, so that members of the cytochrome P450 family are also involved in the metabolism of 25-hydroxycholesterol besides cholesterol 25-hydroxylase.

[3] 25-hydroxycholesterol has been found in various organisms such as mice, rats, rabbits, and cows.