Although the pathogenesis of osteoporosis in inflammatory bowel disease (IBD) is not established, vitamin D deficiency and disturbances in calcium metabolism are thought to be of importance, especially in Crohn disease (CD). Vitamin D status is assessed and the relation between indices of calcium metabolism, including 25-hydroxyvitamin D and parathyroid hormone concentrations. and bone mineral density (BMD) in CD and ulcerative colitis (UC) are examined. Sixty patients with CD and 60 with UC were investigated. Each group comprised 24 men and 36 women.
Vitamin D metabolites, parathyroid hormone and biochemical markers of bone metabolism were measured in blood and urine. Lumbar spine, femoral neck and total body BMD were measured by dual X-ray absorptiometry (DXA) and Z-scores were obtained by comparison with age- and sex-matched normal values.
Vitamin D deficiency (25-hydroxyvitamin D3 <30 nmol/l) was present in 27% of patients with CD and in 15% with UC. Furthermore, CD patients had a significantly lower mean concentration of 25-hydroxyvitamin D3 compared with UC patients. Vitamin D status was not related to BMD at any of the skeletal sites measured. Secondary hyperparathyroidism was found in 10 out of 27 patients with CD after small-bowel resections. No differences were found in serum osteocalcin and urine pyridinoline between patients with CD and those with UC.
Hypovitaminosis D is common in CD patients. Patients with CD and small-bowel resections are at risk of developing secondary hyperparathyroidism and low BMD.