The DHCR24 gene provides instructions for making an enzyme called 24-dehydrocholesterol reductase. This enzyme is involved in multiple pathways that produce cholesterol. Cholesterol is a waxy, fat-like substance that can be obtained from foods that come from animals (particularly egg yolks, meat, poultry, fish, and dairy products). It can also be produced in various tissues in the body. For example, the brain cannot access the cholesterol that comes from food, so brain cells must produce their own. In one pathway, 24-dehydrocholesterol reductase is involved in the final step of cholesterol production (synthesis), converting the fat desmosterol into cholesterol. In a different pathway, 24-dehydrocholesterol reductase converts the fat lanosterol into another fat called 24,25-dihydrolanosterol. The end product of both of these pathways is cholesterol.

Cholesterol is necessary for normal embryonic development and has important functions both before and after birth. Cholesterol is an important component of cell membranes and the fatty protective covering that insulates nerves (myelin). Cholesterol also attaches (binds) to certain proteins to turn on (activate) the hedgehog signaling pathway, which is critical for normal development of many parts of the body before birth. Additionally, cholesterol plays a role in the production of certain hormones and digestive acids.