Biochemical markers (mean ± SD) of vitamin D status, bone turnover and metabolism in patients and controls.

25(OH)D: 25-hydroxyvitamin D, 1,25(OH)2D: 1,25-dihydroxyvitamin D, PTH: parathyroid hormone, DBP: vitamin D binding protein, bALP: bone alkaline phosphatase, NTX: cross-linked N-terminal telopeptide of type 1 collagen (all measured in serum, except NTX that was measured in urine).aEnzyme activity measured in U/l, 1U: one unit of bALP activity was defined as 1 µmol of p-nitrophenyl phosphate hydrolyzed per minute at 25°C,bBCE: Bone Collagen Equivalents,cCr: Creatinine. Comparison of groups was calculated using independent two-tailed t test. CI: mean difference confidence interval.