title: Greater seasonal cycling of 25-hydroxyvitamin D is associated with increased parathyroid hormone and bone resorption.
abstract: CONCLUSIONS
  This analysis assessed whether seasonal change in 25-hydroxyvitamin D concentration was associated with bone resorption, as evidenced by serum parathyroid hormone and C-terminal telopeptide concentrations. The main finding was that increased seasonal fluctuation in 25-hydroxyvitamin D was associated with increased levels of parathyroid hormone and C-terminal telopeptide.
  
  
  BACKGROUND
  It is established that adequate 25-hydroxyvitamin D (25(OH)D, vitamin D) concentration is required for healthy bone mineralisation. It is unknown whether seasonal fluctuations in 25(OH)D also impact on bone health. If large seasonal fluctuations in 25(OH)D were associated with increased bone resorption, this would suggest a detriment to bone health. Therefore, this analysis assessed whether there is an association between seasonal variation in 25(OH)D and bone resorption.
  
  
  METHODS
  The participants were (n = 279) Caucasian and (n = 88) South Asian women (mean (±SD); age 48.2 years (14.4)) who participated in the longitudinal Diet, Food Intake, Nutrition and Exposure to the Sun in Southern England study (2006-2007). The main outcomes were serum 25(OH)D, serum parathyroid hormone (sPTH) and serum C-terminal telopeptide of collagen (sCTX), sampled once per season for each participant.
  
  
  RESULTS
  Non-linear mixed modelling showed the (amplitude/mesor) ratio for seasonal change in log 25(OH)D to be predictive of log sPTH (estimate = 0.057, 95 % CI (0.051, 0.063), p < 0.0001). Therefore, individuals with a higher seasonal change in log 25(OH)D, adjusted for overall log 25(OH)D concentration, showed increased levels of log sPTH. There was a corresponding significant ability to predict the range of seasonal change in log 25(OH)D through the level of sCTX. Here, the corresponding parameter statistics were estimate = 0.528, 95 % CI (0.418, 0.638) and p ≤ 0.0001.
  
  
  CONCLUSIONS
  These findings suggest a possible detriment to bone health via increased levels of sPTH and sCTX in individuals with a larger seasonal change in 25(OH)D concentration. Further larger cohort studies are required to further investigate these preliminary findings.
authors: Department of Nutritional Sciences, School of Biosciences and Medicine, Faculty of Health and Medical Sciences, University of Surrey, Guildford, Surrey, GU2 7XH, UK, a.darling@surrey.ac.uk.
authors: A L
authors: AL
authors: Darling
authors: K H
authors: KH
authors: Hart
authors: M A
authors: MA
authors: Gibbs
authors: F
authors: F
authors: Gossiel
authors: T
authors: T
authors: Kantermann
authors: K
authors: K
authors: Horton
authors: S
authors: S
authors: Johnsen
authors: J L
authors: JL
authors: Berry
authors: D J
authors: DJ
authors: Skene
authors: R
authors: R
authors: Eastell
authors: R
authors: R
authors: Vieth
authors: S A
authors: SA
authors: Lanham-New
mesh_terms: D000328:Adult; D000368:Aged; D001862:Bone Resorption / Q000097:blood* / Q000503:physiopathology; D024042:Collagen Type I / Q000097:blood; D005260:Female; D006801:Humans; D008137:Longitudinal Studies; D008875:Middle Aged; D017711:Nonlinear Dynamics; D010281:Parathyroid Hormone / Q000097:blood*; D010455:Peptides / Q000097:blood; D012621:Seasons; D014807:Vitamin D / Q000031:analogs & derivatives* / Q000097:blood
chemical_list: D024042:Collagen Type I; D010281:Parathyroid Hormone; D010455:Peptides; C052929:collagen type I trimeric cross-linked peptide; D014807:Vitamin D; C104450:25-hydroxyvitamin D
references: Anticancer Res. 2009 Sep;29(9):3713-20
references: 19667169
references: J Bone Miner Res. 2008 Nov;23(11):1789-97
references: 18597628
references: Bone Miner. 1993 Jan;20(1):99-108
references: 8453326
references: FASEB J. 2006 Nov;20(13):2417-9
references: 17023519
references: Int J Cancer. 2004 Sep 1;111(3):468; author reply 469
references: 15221979
references: Bone. 2007 Jun;40(6):1517-28
references: 17395559
references: Bone. 2005 Apr;36(4):654-62
references: 15781002
references: N Engl J Med. 2007 Jul 19;357(3):266-81
references: 17634462
references: J Steroid Biochem Mol Biol. 2007 Mar;103(3-5):620-5
references: 17287117
references: Osteoporos Int. 2011 May;22(5):1389-99
references: 20730415
references: J Bone Miner Res. 2007 May;22(5):757-61
references: 17280528
references: Int J Cancer. 2004 Jan 1;108(1):104-8
references: 14618623
references: Osteoporos Int. 2013 Feb;24(2):477-88
references: 22525977
references: Scand J Clin Lab Invest. 2010 Jul;70(4):281-6
references: 20429698
references: Lancet. 1977 May 7;1(8019):979-80
references: 67470
references: BMC Public Health. 2009 Jan 19;9:22
references: 19152676
references: Lupus. 2012 Jul;21(8):855-64
references: 22433915
references: Bone. 2006 Sep;39(3):598-608
references: 16600704
references: Osteoporos Int. 2009 Nov;20(11):1807-20
references: 19543765
references: Anticancer Res. 2009 Sep;29(9):3675-84
references: 19667164
references: J Steroid Biochem Mol Biol. 2010 Jul;121(1-2):462-6
references: 20399270
references: Eur J Clin Nutr. 1992 Jul;46(7):509-15
references: 1623855
references: Acta Paediatr. 1997 Sep;86(9):1006-8
references: 9343285
references: Am J Clin Nutr. 2010 Oct;92(4):841-8
references: 20720256
references: J Clin Endocrinol Metab. 1998 Jan;83(1):68-75
references: 9435418
references: Osteoporos Int. 2009 Jan;20(1):133-40
references: 18458986
references: J Bone Miner Res. 2003 Jul;18(7):1274-81
references: 12854838