Vitamin D status and measurements of markers of bone metabolism in patients with small intestinal resection

Background and aims: Vitamin D deficiency is common in patients with small intestinal resection and may lead to secondary hypersecretion of parathyroid hormone (PTH), which in turn may result in increased bone turnover rate and loss of bone mineral. The aims of this study were to investigate the prevalence of vitamin D deficiency, as assessed by low serum concentrations of 25-hydroxyvitamin D (25(OH)D) in patients with small intestinal resection and to explore the relation of 25(OH)D to PTH, markers of bone turnover rate, and bone mineral density (BMD) in these patients. Patients: Forty two patients with small intestinal resection, a faecal energy excretion of more than 2.0 MJ/day, and a mean length of the remaining small intestine of 199 cm were included. Diagnoses were Crohn's disease (n=35) and other (n=7). Methods: 25(OH)D was analysed by radioimmunoassay and bone turnover rate was assessed by measurement of serum osteocalcin, serum alkaline phosphatase, urine pyridinoline, and urine deoxypyridinoline. BMD was measured by dual energy x ray absorptiometry. Results: Mean 25(OH)D concentration was 13.4 (SD 9.7) ng/ml, which was significantly below the reference mean of 26.4 (SD 13.2) ng/ml (p<0.001). Vitamin D deficiency (25(OH)D concentration <= 8 ng/ml) was found in 38.1% of patients and was accompanied by raised concentrations of PTH and significantly increased markers of bone resorption (p<0.05). Low 25( OH) D concentrations correlated significantly with lower BMD z scores of the spine (r=0.38; p=0.02) and hip (r=0.33; p=0.04). Conclusions: We found reduced 25(OH)D concentrations in patients with small intestinal resection, and showed that a deficient 25(OH)D concentration is associated with significantly increased markers of bone resorption and decreased BMD values.