24S-Hydroxycholesterol (24S-HC), also known as cholest-5-ene-3,24-diol or cerebrosterol, is an endogenous oxysterol produced by neurons in the brain to maintain cholesterol homeostasis.

[4] 24S-HC binds to apolipoproteins such as apoE, apoJ, and apoA1 to form HDL-like complexes[5] which can cross the blood–brain barrier more easily than free cholesterol.

[1][6] After entering general blood circulation and traveling to the liver, 24S-HC can be sulfated, glucuronidated, or converted into bile acids, which can ultimately be excreted.

[8] 24S-HC may participate in several aspects of brain development and function, such as axon and dendrite growth or synaptogenesis,[4] as well as acting as a positive allosteric modulator of NMDA receptors.

[9] Regulation of 24S-HC metabolism in neurons may play a role in their health and function, as well as their response to injury or disease.