7-dehydro Cholesterol-d7 is intended for use as an internal standard for the quantification of 7-dehydro cholesterol by GC- or LC-MS. 7-dehydro Cholesterol (7-DHC) is an immediate precursor of cholesterol.[1] It is reduced to cholesterol by the enzyme 3β-hydroxysterol-Δ7-reductase (DHCR7) in the last step of cholesterol biosynthesis. It accumulates in Smith-Lemli-Opitz syndrome (SLOS), a disorder characterized by a mutation in the DHCR7 gene and decreased cholesterol levels in bodily tissues and fluids, as well as microcephaly, intellectual disability, and distinctive dysmorphic features.[1],[2] 7-DHC is highly susceptible to free radical oxidation, giving rise to several oxysterols that may be involved in the pathogenesis of SLOS.[1] 7-DHC levels are increased in brain, liver, and serum in a rat model of SLOS induced by the DHCR7 inhibitor AY 9944.1 7-DHC is also a provitamin that is converted to vitamin D3 by ultraviolet-B (UVB) light in a human skin equivalent system and in isolated human skin samples.[3],[4].

Reference:
[1]. Xu, L., Liu, W., Sheflin, L.G., et al. Novel oxysterols observed in tissues and fluids of AY9944-treated rats: A model for Smith-Lemli-Opitz syndrome. Journal of Lipid Research 52, 1810-1820 (2011).
[2]. Xu, G., Salen, G., Shefer, S., et al. Reproducing abnormal cholesterol biosynthesis as seen in the Smith-Lemli-Opitz syndrome by inhibiting the conversion of 7-dehydrocholesterol to cholesterol in rats. Journal of Clinical Investigation 95(1), 76-81 (1995).
[3]. Lehmann, B., Genehr, T., Knuschke, P., et al. UVB-induced conversion of 7-dehydrocholesterol to 1α,25-dihydroxyvitamin D3 in an in vitro human skin equivalent model. Journal of Investigative Dermatology 117(5), 1179-1185 (2001).
[4]. Chen, T.C., Chimeh, F., Lu, Z., et al. Factors that influence the cutaneous synthesis and dietary sources of vitamin D. Archives of Biochemistry and Biophysics 460(2), 213-217 (2007).