[Metabolism and main effects of vitamin D].
Vitamin D is not a vitamin stricto sensu as its main source does not come from diet. Vitamin D should rather be considered as a prohormone. To become fully active, vitamin D must be hydroxylated into 25(OH)D in the liver and then into 1,25(OH)2D (also called calcitriol) in the kidney, but also in many other tissues. The main classical effects of vitamin D concern bone and calcium/phosphorus metabolism. Many non-classical effects of vitamin D are suggested by the quasi-ubiquitous presence of the vitamin D receptor and by myriads of studies showing an association between vitamin D deficiency/insufficiency and an increased incidence or a poor prognostic of many diseases. The 25(OH)D serum concentration is the biological index that defines vitamin D status. There is currently no absolute consensus on the definition of vitamin D deficiency. Many experts consider that a 25(OH)D level less than 50 nmol/L corresponds to vitamin D deficiency whereas a concentration between 50 and 75 nmol/L corresponds to vitamin D insufficiency. These definitions are mostly based on the musculoskeletal effects of vitamin D.
Hôpital Necker-Enfants-Malades, service d'explorations fonctionnelles, 75015 Paris, France. Electronic address: jean-claude.souberbielle@nck.aphp.fr.
Jean-Claude
JC
Souberbielle
Gérard
G
Maruani
Marie
M
Courbebaisse
D000818:Animals; D003940:Diagnostic Techniques, Endocrine / Q000592:standards; D004032:Diet; D006801:Humans; D008954:Models, Biological; D018167:Receptors, Calcitriol / Q000378:metabolism / Q000502:physiology; D014807:Vitamin D / Q000097:blood / Q000378:metabolism* / Q000494:pharmacology*; D014808:Vitamin D Deficiency / Q000097:blood / Q000175:diagnosis*
D018167:Receptors, Calcitriol; D014807:Vitamin D