Vitamin D

摘要: Abstract Vitamin D is the major regulator of calcium homeostasis in body and critically important for normal mineralization bone to prevent rickets children osteomalacia adults. The active hormone, 1α,25-dihydroxyvitamin D3 (1,25(OH)2D3, also called calcitriol), produced by sequential hydroxylations vitamin liver (25-hydroxylation) kidney (1α-hydroxylation). 1,25(OH)2D3 acting via receptor (VDR), functions a genomic mechanism similar classical steroid hormones regulate target gene transcription. traditional actions are enhance phosphate absorption from intestine order maintain mineral concentrations circulation provide adequate amounts these minerals bone-forming sites allow proceed normally. However, since early 1990s, it has become increasing clear that many additional extraskeletal implicate hormone wide array unrelated or metabolism. It now known modulates activity hundreds, if not thousands, genes essentially every tissue making potent critical processes. Some can be categorized as antiproliferative, prodifferentiating, immunosuppressive, anti-inflammatory. In this chapter, we will describe basic biology including its metabolism, physiology, action, diverse those relate metabolism well newer actions. Several reviews action function have been published new edition comprehensive book addressing all areas biology. Specific issues relating osteoporosis discussed Chapter 73.