 This enzyme is involved in the initial stages of the synthesis of bile acids from cholesterol and a member of the short-chain dehydrogenase/reductase superfamily.This enzyme is a membrane-associated endoplasmic reticulum protein which is active against 7-alpha hydrosylated sterol substrates.Mutations in the HSD3B7 gene are associated with a congenital bile acid synthesis defect which leads to neonatal cholestasis, a form of progressive liver disease.