7-dehydrocholesterol reductase of the cholesterol biosynthetic pathway reducing the C7-C8 double bond of cholesta-5,7-dien-3beta-ol (7-dehydrocholesterol/7-DHC) and cholesta-5,7,24-trien-3beta-ol, two intermediates in that pathway. cholesterol + NADP(+) = 7-dehydrocholesterol + H(+) + NADPH 7-dehydrodesmosterol + H(+) + NADPH = desmosterol + NADP(+) Steroid biosynthesis; cholesterol biosynthesis. Interacts with DHCR24; this interaction regulates DHCR7 activity. Widely expressed. Most abundant in adrenal gland, liver, testis, and brain. The disease is caused by variants affecting the gene represented in this entry. Belongs to the ERG4/ERG24 family.