Longitudinal study of vitamin D metabolites after long bone fracture.
Briggs ADM., Kuan V., Greiller CL., Maclaughlin BD., Ramachandran M., Harris T., Timms PM., Venton TR., Vieth R., Norman AW., Griffiths CJ., Martineau AR.
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]₂D) after long bone fracture. Human studies investigating the kinetics of serum concentrations of 24R,25[OH]₂D, 1,25-dihydroxyvitamin D (1,25[OH]₂D) 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 after 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)₂D, 1,25(OH)₂D, vitamin D binding protein, albumin, and calcium were determined within 48 hours of fracture and again at 1 and 6 weeks postfracture. 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)₂D were seen at either follow-up time point versus baseline. In 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