maoudoody
Forum Elite
Topics: 20
Posts: 372
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dr Goljan says that cytochrome inducers like chronic alcohol , phenytoin could cause vitamin d deffeciency
but i dont know why ....inducing cytochrome will accelerate 25 hydroxylation of vitamin d so it is supposed to increase not decrease
can anyone explain this?
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| Tiff
Forum Guru
Topics: 49
Posts: 500
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According to Goljan, precursors of 25-(OH)-D have increased metabolism with induction of cytochrome P450.
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| maoudoody
Forum Elite
Topics: 20
Posts: 372
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but he said that the liver hydroxylation of vitamin d occurs in the cytochrome p450 system?
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| Tiff
Forum Guru
Topics: 49
Posts: 500
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Hmmm. Your right. P450 is major for clearing Vitamin D. I think it has to do with different methods of hydroxylation for metabolizing it and clearing it. I'll have to look it up.
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| Tiff
Forum Guru
Topics: 49
Posts: 500
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"1,25(OH)2D increases the expression of 25-hydroxyvitamin D-24-hydroxylase (24-OHase) to catabolize 1,25(OH)2D to the water-soluble, biologically inactive calcitroic acid, which is excreted in the bile." http://www.uvadvantage.org/portals/0/pdf/NEJourna... What I gather is that hydroxylation is enhanced with these inducers...meaning 25 hydroxylation as well as 24-hydroxylation (which is used for clearing it). The more 1,25 OH produced will also increase 24- OHase to break down Vitamin D to an inactive form for clearance. Also the last couple of lines of pg.328-329 might help. http://www.biochemj.org/bj/347/0321/3470321.pdf.
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