title: [Vitamin D3--a prodrug of different D3-hormones].
abstract: Vitamin D (colecalciferol) is critically important for the development, growth, and maintenance of a healthy skeleton from birth until death. Vitamin D is metabolized in the liver to 25-hydroxy-colecalciferol and then in the kidney to 1 alpha,25-dihydroxy-colecalciferol (calcitriol). Calcitriol is the dominant D(3)-hormone and produces a wide array of bio-logical responses via interacting both with the classical vitamin D nuclear receptor (VDR(nuc)) that regulates gene transcription in over 30 target organs and with a putative cell membrane receptor (VDR(mem1,25)) that mediates rapid biological responses. 24R,25-Dihydroxy-colecalciferol has been shown to be an essential D(3)-hormone for the process of bone fracture healing. It initiates its biological responses via stereospecific binding to a second cell membrane receptor, the VDR(mem24,25). The key D(3)-hormone involved in the regulation of cell proliferation in the prostate is 25-hydroxy-colecalciferol. It is mainly acting directly through the nuclear vitamin D receptor but partially also through its 1 alpha-hydroxylation in the prostate. Elderly subjects often have mean 25-hydroxy-colecalciferol levels in the insufficiency range throughout the year. The oral dose necessary to achieve adequate serum 25-hydroxy-colecalciferol levels is a daily dose of 400 IU.
authors.affiliation: Institut für Pharmazie, Freie Universität Berlin, Berlin, Germany. sieker@zedat.fu-berlin.de
authors.forename: Walter
authors.initials: W
authors.lastname: Schunack
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D050071:Bone Density Conservation Agents; D002117:Calcitriol / Q000502:physiology*; D002762:Cholecalciferol; D005260:Female; D005504:Food Analysis; D006801:Humans; D008297:Male; D008875:Middle Aged; D015663:Osteoporosis, Postmenopausal / Q000378:metabolism; D011355:Prodrugs; D018167:Receptors, Calcitriol / Q000502:physiology; D014807:Vitamin D / Q000032:analysis / Q000502:physiology; D014808:Vitamin D Deficiency / Q000378:metabolism
chemical_list: D050071:Bone Density Conservation Agents; D011355:Prodrugs; D018167:Receptors, Calcitriol; D014807:Vitamin D; D002762:Cholecalciferol; D002117:Calcitriol