The effect of trauma on serum concentrations of vitamin D metabolites in patients with hip fracture.

In a previous study we observed lower serum concentrations of 25(OH)D, 24,25(OH)2D, and 1,25(OH)2D in patients with hip fracture than in aged control subjects. In order to evaluate the effect of trauma on vitamin D metabolite levels, we measured serum concentrations of vitamin D binding protein (DBP) in 118 patients with hip fracture and 71 aged control subjects. Serum DBP was lower in the patients than in the controls (mean +/- SD 315 +/- 60 vs 371 +/- 44 mg/l, P less than 0.001). Serum DBP correlated positively with serum total protein, albumin, alpha 2-globulin, and the vitamin D metabolite levels in the patients. When correcting for differences in serum DBP, serum 25(OH)D and 24,25(OH)2D still were significantly lower in patients than in controls, whereas serum 1,25(OH)2D was not. The free 1,25(OH)2D index (10(5) x molar ratio 1,25(OH)2D/DBP) was lower in patients than in controls, but the level of significance was marginal. This difference was not significant when patients and controls with impairment of renal function were excluded. It is concluded that the difference in serum 25(OH)D and 24,25(OH)2D between patients and controls is largely preexistent. However, the lower serum 1,25(OH)2D in the patients is mainly caused by the trauma. The free 1,25(OH)2D concentrations are almost similar in the two groups when renal function is normal.