25-Hydroxyvitamin D3 1-alpha-Hydroxylase25-Hydroxyvitamin D 2CalcifediolVitamin DVitamin D DeficiencyCholecalciferolHydroxycholecalciferolsErgocalciferolsDihydroxycholecalciferols24,25-Dihydroxyvitamin D 3Steroid HydroxylasesParathyroid HormoneCalcitriolVitamin D-Binding ProteinRicketsSunlightCell ProliferationCholestanetriol 26-MonooxygenaseReceptors, CalcitriolSeasonsDietary SupplementsVitaminsCalcium, DietaryPhosphorusOsteomalaciaCalciumBone DensityHydroxylationCross-Sectional StudiesNutritional StatusSkin PigmentationBone and BonesCells, CulturedCytochrome P-450 Enzyme SystemBiological MarkersKidneyRisk FactorsLinear ModelsProspective StudiesBone Density Conservation AgentsChromatography, High Pressure LiquidCase-Control StudiesCell DivisionCell DifferentiationDietRNA, MessengerFood, FortifiedEuropean Continental Ancestry GroupCohort StudiesSignal TransductionCell Line, TumorCholestenesTime FactorsPrevalenceDehydrocholesterolsHypoparathyroidismDose-Response Relationship, DrugPhosphatesNutritional RequirementsAlkaline PhosphataseApoptosisNutrition SurveysRadioimmunoassayAfrican AmericansTandem Mass SpectrometryMass SpectrometryAbsorptiometry, PhotonBody Mass IndexBostonHypercalcemiaCell CycleNutrition PolicyOsteoporosisFractures, BoneChromatography, LiquidPostmenopauseIntestinal AbsorptionAdrenodoxinDouble-Blind MethodCell LineUnited StatesNebraskaHyperparathyroidism, SecondaryOsteocalcinPregnancyBlotting, WesternChickensReverse Transcriptase Polymerase Chain ReactionSpectrophotometry, UltravioletHyperparathyroidismMultivariate AnalysisLogistic ModelsMilkHypocalcemiaLymphocyte ActivationBromodeoxyuridineMice, Inbred C57BLKineticsMongoliaReference Values