title: Vitamin D deficiency, bone turnover markers and causative factors among adolescents: a cross-sectional study.
abstract: BACKGROUND
  This cross-sectional population-based study was conducted to elucidate the prevalence of vitamin D deficiency, bone turnover marker's variation and its influencing factors among adolescents of Tehran.
  
  
  METHODS
  Totally 444 middle and high school (53.6 % in high school) students (both girls and boys) were recruited. A short food frequency questionnaire designed to estimate dietary calcium and vitamin D consumption. Serum levels of calcium, phosphorus, parathyroid hormone (PTH), bone specific alkaline phosphates, 25 (OH) vitamin D, osteocalcin, cross-linked C-telopeptide (CTX), total protein, albumin and creatinine were determined.
  
  
  RESULTS
  Vitamin D deficiency was prevalent in adolescents and only 22.4 % of students had normal serum vitamin D. Results revealed that vitamin D insufficiency reported in 34.2 % of students and vitamin D deficiency was in 43.3 % of them. Serum vitamin D, osteocalcin, CTX and bone specific alkaline phosphates were significantly higher in boys in all different ages. Serum levels of 25 (OH) vitamin D had positive influences on bone turnover markers and had negative correlation with PTH.
  
  
  CONCLUSIONS
  Vitamin D deficiency and insufficiency is common among healthy adolescents of Tehran. There is a pressing need to improve vitamin D status among adolescents. Increasing vitamin D fortification of dairy products can be considered as a population-wide public health strategy in Iran.
authors.affiliation: Osteoporosis Research Center, Endocrinology and Metabolism Clinical Sciences Institute, Tehran University of Medical Sciences, 5th floor, shariati Hospital, North Kargar, Tehran, 141142386 Iran.
authors.forename: Bagher
authors.initials: B
authors.lastname: Larijani
authors.affiliation: Osteoporosis Research Center, Endocrinology and Metabolism Clinical Sciences Institute, Tehran University of Medical Sciences, 5th floor, shariati Hospital, North Kargar, Tehran, 141142386 Iran.
authors.forename: Arash
authors.initials: A
authors.lastname: Hossein-Nezhad
authors.affiliation: Osteoporosis Research Center, Endocrinology and Metabolism Clinical Sciences Institute, Tehran University of Medical Sciences, 5th floor, shariati Hospital, North Kargar, Tehran, 141142386 Iran.
authors.forename: Elham
authors.initials: E
authors.lastname: Feizabad
authors.affiliation: Osteoporosis Research Center, Endocrinology and Metabolism Clinical Sciences Institute, Tehran University of Medical Sciences, 5th floor, shariati Hospital, North Kargar, Tehran, 141142386 Iran.
authors.forename: Zhila
authors.initials: Z
authors.lastname: Maghbooli
authors.affiliation: Osteoporosis Research Center, Endocrinology and Metabolism Clinical Sciences Institute, Tehran University of Medical Sciences, 5th floor, shariati Hospital, North Kargar, Tehran, 141142386 Iran.
authors.forename: Hossein
authors.initials: H
authors.lastname: Adibi
authors.affiliation: Osteoporosis Research Center, Endocrinology and Metabolism Clinical Sciences Institute, Tehran University of Medical Sciences, 5th floor, shariati Hospital, North Kargar, Tehran, 141142386 Iran.
authors.forename: Majid
authors.initials: M
authors.lastname: Ramezani
authors.affiliation: Osteoporosis Research Center, Endocrinology and Metabolism Clinical Sciences Institute, Tehran University of Medical Sciences, 5th floor, shariati Hospital, North Kargar, Tehran, 141142386 Iran.
authors.forename: Eghbal
authors.initials: E
authors.lastname: Taheri
keywords: Adolescents; Bone turnover markers; Vitamin D deficiency