J Bone Miner Res. 2012 Dec 21. doi: 10.1002/jbmr.1855.
Briggs AD, Kuan V, Greiller CL, Maclaughlin BD, Ramachandran M, Harris T, Timms PM, Venton TR, Vieth R, Norman AW, Griffiths CJ, Martineau AR.
Centre for Primary Care and Public Health, Barts and The London School of Medicine and Dentistry, Queen Mary University of London, London E1 2AB, UK.
Animal models suggest a key role for dihydroxylated vitamin D metabolites in fracture healing, as evidenced by increases in serum concentration of 24R,25-dihydroxyvitamin D (24R,25[OH](2) D) following long bone fracture. Human studies investigating the kinetics of serum concentrations of 24R,25[OH](2) D, 1,25-dihydroxyvitamin D (1,25[OH](2) D) and their parent metabolite 25-hydroxyvitamin D (25[OH]D) are lacking. We therefore conducted a longitudinal study to determine whether total, free or bioavailable concentrations of these vitamin D metabolites fluctuate in humans following long bone fracture.
Twenty-eight patients with cross-shaft (diaphyseal) long bone fracture presenting to an Emergency Department in London, UK, were studied. Serum concentrations of 25(OH)D, 24R,25(OH)(2) D, 1,25(OH)(2) D, vitamin D binding protein, albumin and calcium were determined within 48 hours of fracture, and again at one and six weeks post-fracture. Concentrations of free and bioavailable vitamin D metabolites were calculated using standard equations.
No changes in mean serum concentrations of 25(OH)D or 24R,25(OH)(2) D were seen at either follow-up time point vs. baseline.
By contrast, mean serum 1,25(OH)(2) D concentration declined by 21% over the course of the study, from 68.5 pmol/L at baseline to 54.1 pmol/L at 6 weeks (p < 0.05).
This decline was associated with an increase in mean serum corrected calcium concentration, from 2.32 mmol/L at baseline to 2.40 mmol/L at one week (p < 0.001), that was maintained at 6 weeks.
No changes in free or bioavailable concentrations of any vitamin D metabolite investigated were seen over the course of the study.
We conclude that serum 1,25(OH)(2) D concentration declines following long bone fracture in humans, but that the serum 24R,25(OH)(2) D concentration does not fluctuate.
The latter finding contrasts with those of animal models reporting increases in serum 24R,25(OH)(2) D concentration following long bone fracture. © 2012 American Society for Bone and Mineral Research.
Copyright © 2012 American Society for Bone and Mineral Research.