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Graphical description of vitamin D synthesis in humans

Legend: CYP24A1 = cytochrome P450 2741, commonly known as 1,25-dihydroxyvitamin D3 24-hydroxylase; CYP27A1 = cytochrome P450 27A1, commonly known as sterol 27-hydroxylase; CYP27B1 = cytochrome P450 27B1, commonly known as 25-hydroxyvitamin D3 1-alpha-hydroxylase; CYP2R1 = cytochrome P450 2R1, commonly known as vitamin D 25-hydroxylase; DHCR7 = 7-dehydrocholesterol reductase; RXRA = retinoid X receptor alpha; RXRB = retinoid X receptor beta; VDR = vitamin D receptor. Source: Pico A, Evelo C, Riberio L, van Iersel M, Hanspers K (2010). (Courtesy of Wikimedia Commons. Creative Commons Attribution-Share Alike 3.0 Unported license.)