Michèle Garabédian

Prophylaxie de la carence en vitamine D chez l'adolescent et le préadolescent. Étude interventionnelle multicentrique sur les effets biologiques d'un apport répété de 100 000 UI de vitamine D3

Resume Des etudes recentes ont attire lattention des pediatres sur les risques de carence calcique et vitaminique D dans la periode de la preadolescence et de ladolescence. Lobjectif de cette etude interventionnelle multicentrique a ete de comparer leffet dune administration trimestrielle de vitamine D sur le statut vitaminique D et le metabolisme calcique dans une population de quatre centres universitaires situes au nord de la Loire. Population et methodes Deux groupes de preadolescents et adolescents de dix a 15 ans ont ete suivis entre octobre 1996 et juillet 1997. Apres un premier bilan clinique, radiologique et phosphocalcique commun (j0), le premier groupe (n = 33) a recu 100 000 UI de vitamine D tous les trois mois entre octobre et juin, le second un placebo (n = 35). Des controles cliniques et biologiques ont ete effectues trois mois apres la premiere prise (bilan intermediaire, jl) et la troisieme prise (bilan final, JF). Un second controle radiologique du poignet gauche a ete effectue lors du bilan final, soit apres six a neuf mois de traitement. Resultats A linclusion (octobre-decembre), 16 enfants sur 68 avaient des concentrations circulantes en 25-hydroxyvitamine D (25-(OH)D) inferieures ou egales a 10 ng/mL, six des valeurs tres basses (inferieures a 6 ng/mL). Une variation significative des concentrations en 25-(OH)D avec le stade pubertaire des enfants etait retrouvee ; les taux les plus bas ont ete observes en fin de puberte (stade pubertaire IV). Au controle intermediaire (trois mois apres la premiere prise) et en fin detude, pour lensemble du groupe placebo, les evolutions des concentrations en 25-(OH)D netaient pas significatives. En revanche, une elevation des concentrations en iPTH a 34 ± 11 pg/ mL etait observee ; 14 % des adolescents avaient des taux de iPTH superieurs a 50 pg/mL en fin detude (versus 8 % en debut detude et a jl). Pour le groupe ayant recu la supplementation vitaminique D tous les trois mois, les valeurs moyennes de 25-(OH)D sont restees superieures a 20 ng/mL ; aucune hypercalcemie na ete observee et les concentrations en iPTH mesurees en fin detude sont en moyenne de 25 ± 14 pg/mL. Conclusion Meme en fin dete, un pourcentage significatif de preadolescents presente des valeurs de 25-(OH)D evoquant une carence biologique en vitamine D. Levolution des concentrations en iPTH suggere que cette carence saggrave au cours de lhiver. La supplementation orale de 100 000 UI de vitamine D tous les trois mois entre octobre et juin compense cette baisse saisonniere des reserves en vitamine D.UNLABELLEDnRecent studies have shown a high prevalence of calcium and vitamin D deficiencies in adolescents. The aim of this present study was to follow the changes in calcium status and 25 hydroxyvitamin D (25[OH]D) and parathyroid hormone (iPTH) levels during winter in preadolescents and adolescents from four university hospitals in northern France.nnnSUBJECTS AND METHODSnTwo groups of teenagers and adolescents (range: 10-15 years) were followed from October 1996 to June 1997. They were given either 100,000 IU of vitamin D (treated group n = 33) or a placebo (control group n = 35) in October, January and April. Serum calcium, phosphate, 25(OH)D and iPTH levels were measured at inclusion and every three months thereafter.nnnRESULTSnAt inclusion, plasma or serum 25(OH)D levels were < or = 10 ng/mL in 16 subjects and < 6 ng/mL in six. In control children, no significant change in 25(OH)D occurred during the study, while plasma or serum iPTH levels increased to 34 +/- 11 pg/mL. In the treated groups, 25(OH)D levels remained > 20 ng/mL in every subject; no hypercalcemia was observed; and the mean plasma or serum iPTH level was 25 +/- 14 pg/mL at the end of the study.nnnCONCLUSIONnTeenagers presented with a high prevalence of biological vitamin D deficiency at the end of summer. The increase of iPTH during winter in the unsupplemented group suggests that this has secondary consequences on their calcium homeostasis unless they are supplemented with vitamin D. We advocate a sufficient calcium supply and a 100,000 IU vitamin D supplement given two or three times during winter to preadolescents and adolescents living in northern France.

Prévention de la carence en vitamine D chez l'enfant et l'adolescent I. Proposition et argumentaire pour l'utilisation d'un abaque décisionnel

Resume Il existe peu de donnees epidemiologiques specifiques sur lincidence de la carence en vitamine D chez lenfant et ladolescent. Le taux de 25-hydroxyvitamine D circulant [25-(OH) D], au-dessous duquel il y a un risque de carence, se situe a 10–12 ng/mL pour le nouveau-ne et la personne âgee, mais ce chiffre ne peut pas etre extrapole avec certitude aux grands enfants et aux adolescents. En fin dhiver en France, 14 a 35 % dentre eux ont un taux de 25-(OH) D inferieur a cette limite. Mais seuls ceux ayant un taux inferieur a 3 ng/mL ont un trouble du metabolisme calcique (hypocalcemie, augmentation du taux de parathormone serique), pouvant avoir des consequences sur la mineralisation du squelette. Le dosage systematique des parametres biologiques dans un but de depistage netant pas possible, un abaque decisionnel (fonde sur des donnees biologiques et epidemiologiques) est propose pour identifier les populations a risque de statut vitaminique D faible. Cet abaque utilise trois questionnaires. Le premier concerne lexposition solaire et evalue la synthese endogene de vitamine D en tenant compte du temps ecoule depuis lexposition. Le second quantifie les apports alimentaires de vitamine D selon un score a trois niveaux : optimal, moyen ou bas. En cas dapport alimentaire moyen, le troisieme questionnaire est necessaire pour quantifier les apports calciques, des apports calciques faibles (moins de 400 mg/j) accelerant le catabolisme de la vitamine D. Cet abaque devrait permettre de depister, de facon simple, les enfants et adolescents a risque de carence en vitamine D afin de mettre en place une prophylaxie adaptee. Sa justesse devra etre evaluee lors denquetes prospectives ulterieures.

Recommandations pour la prise en charge de la déminéralisation osseuse dans la mucoviscidose

A high prevalence of low bone mineralization is documented in adult patients with cystic fibrosis (CF). Osteopenia is present in as much as 85% of adult patients and osteoporosis in 13 to 57% of them. In children, studies are discordant probably because of different control database. Denutrition, inflammation, vitamin D and vitamin K deficiency, altered sex hormone production, glucocorticoid therapy, and physical inactivity are well known risk factors for poor bone health. Puberty is a critical period and requires a careful follow-up for an optimal bone peak mass. This review is a consensus statement established by the national working group of the French Federation of CF Centers to develop practice guidelines for optimizing bone health in patients with CF. Recommendations for screening and for calcium, vitamin D and K supplementation are given. Further work is needed to define indications for treatment with biphosphonates and anabolic agents.

Biological Effects of Supplementation with Vitamin D and Calcium in Postmenopausal Women with Low Bone Mass Receiving Alendronate

ObjectiveTo investigate the biological effects of supplementation with vitamin D and calcium versus supplementation with calcium alone during the first 3 months of treatment with alendronate in postmenopausal women with a risk of fracture and with vitamin D and calcium insufficiency.DesignRandomised, double-blind trial.SubjectsThe study randomised 48 osteopenic and osteoporotic women, mean age 70 ± 6 years and at least 5 years after menopause, who were living at home. Inclusion criteria were low bone mineral density (more than 1 SD below reference value), serum 25-hydroxy-vitamin D3 (25-OHD, calcifediol) <12 μg/L and dietary calcium intake <1 g/day.MethodsThe women were divided into two groups. The first group (n = 23) received alendronate 10mg once daily supplemented with calcium and vitamin D (elemental calcium 500mg, colecalciferol [vitamin D3] 400IU) twice daily for 3 months. The second group (n = 25) received the same dosage of alendronate and a placebo with calcium alone (500 mg/day). Blood, serum and urine samples were obtained for measurement of calcaemia, intact parathyroid hormone (i-PTH) and markers of bone remodelling such as the N- and C-terminal telopeptides of type I collagen (NTX and CTX).ResultsSupplementation with calcium and vitamin D caused a rapid increase of 25-OHD levels without changes in calcaemia or i-PTH levels. In the two groups, serum and urinary CTX and urinary NTX were dramatically and significantly decreased after as little as 15 days of treatment and remained decreased throughout the course of treatment. No significant difference between the two treatments was observed, but the combined treatment resulted in a more pronounced effect as assessed by the Hodge-Lehman test, particularly after 1 month for the bone resorption markers serum CTX (p = 0.064) and urinary NTX (p = 0.076).ConclusionSupplementation with calcium and vitamin D could be appropriate in elderly women with calcium and vitamin D insufficiencies being treated with alendronate in order to achieve rapid reduction of bone remodelling.