(3β)-7-Dehydro Cholesterol-d7 is a labelled analogue of (3β)-7-Dehydro Cholesterol (D229455). (3β)-7-Dehydro Cholesterol is a vitamin D3 precursor, and is also a precursor to the biosynthesis of cholesterol in the body. Accumulation of (3β)-7-Dehydro Cholesterol and low levels of plasma cholesterol levels are characteristic of a recessive birth defect disease called Smith-Lemli-Opitz syndrome.