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1、RicketsofvitaminDdeficiencyDr.YanHaoDeptofPediatricsTongjiHospital,HUSTTel:83662684e-mail:haoyaner@163.comRicketsThetermricketsevolvedfromtheoldEnglishwordwrick,meaningtotwist.Thistwistingorbendingoftheboneshasbeenknownsinceantiquityandwasdescribedindetailby
2、F.Glissonin1650atermsignifyingfailuretomineralizegrowingboneorosteoidtissuemanycauses,mainlyvitaminDdeficiencySynonymofrachitisVitaminDFatsoluble,stabletoheat,acidalkali,andoxidationbilenecessaryforabsorptionIn1824,cod-liveroilwasfirstlybeprescribedforthetre
3、atmentofricketsbyD.Scheutte.In1906,Hopkinspostulatedtheexistenceofessentialdietaryfactorsnecessaryforthepreventionofrickets.In1928,theNobelprizeforchemistrywasawardedtoAdolfWindausforhisdiscoveryofvitaminD.Ergosterol麦角甾醇calciferolorvitaminD-2麦角骨化醇7-dehydroch
4、olesterol7-脱氢胆固醇cholecalciferolorvitaminD3胆骨化醇sunlightsunlightplantskinabsorpableblood1-alpha-hydroxylase↑25-alpha-hydroxylasePTHLowP3-VitaminDactuallyreferstoagroupofsteroidmoleculesTwoforms:vitaminD2(calciferol)andvitaminD3(cholecalciferol)Bothareproduceds
5、yntheticallyandareavailableasdietarysupplementsEachoftheformsofvitaminDishydrophobic,andistransportedinbloodboundtocarrierproteins,mainlyvitaminD-bindingprotein.Thehalflifeof25-hydroxycholecalciferolisseveralweeks,whilethatof1,25-dihydroxycholecalciferolison
6、lyafewhours.1,25-dihydroxycholecalciferolReceptorsarepresentinmostcellsifnotallmostdramaticeffectistofacilitateintestinalabsorptionofcalcium,althoughitalsostimulatesabsorptionofphosphateandmagnesiumionsfacilitaterenalreabsorptionofphosphoruspossiblyadirectef
7、fectonbonedepositionandreabsorptionofcalciumandphosphorusCoordinatedwithparathormone(PTH)andcalcitoninTheVitaminDReceptorandMechanismofActionTheactiveformofvitaminDbindstointracellularreceptorswhichformsheterodimerwithanotherintracellularreceptor,theretinoid
8、-Xreceptor,andbindstoDNAtomodulategeneexpressionInmostcasesstudied,theeffectistoactivatetranscription,butsituationsarealsoknowninwhichvitaminDsuppressestranscription.affinityfor1,25-dihydroxycho
