Increased urinary N-telopeptide cross-linked type 1 collagen predicts boneloss in patients with inflammatory bowel disease

OBJECTIVE: Reduced bone mineral density (BMD) is common in patients with in flammatory bowel disease (IBD), but the factors associated with its longitu dinal rate of change have not been established. We prospectively assessed t he rate of change in BMD, and its association with biochemical markers of b one turnover. METHODS: Twenty-two patients with Crohn's disease and 14 ulcerative colitis patients age 37.1 +/- 11.6 yr were followed for 2 yr. Lumbar spine (L2-L4) and femoral neck BMD were measured by dual x-ray absorptiometry at baselin e and 24 months. Bone-specific alkaline phosphatase, osteocalcin, urinary N -telopeptide crosslinked type 1 collagen (NTx), parathyroid hormone, and 25 -hydroxyvitamin-D were determined at baseline. RESULTS: At baseline, 59% of Crohn's patients and 43% of ulcerative colitis patients were osteoporotic, with spine or femoral neck BMD T-score <-2.5. Spine BMD, and spine and femoral neck T-scores were lower and disease durat ion was longer in nine patients with ileal resection compared with nonopera ted patients (0.84 +/- 0.15 g/cm(2) vs 0.96 +/- 0.11 g/cm(2), -3.0. +/- 1.5 vs -1.7 +/- 1.3, -3.2 +/- 1.5 vs -2.2 +/- 1.0, respectively; all p < 0.05) . At 24 months, 13/36 (36%) and 14/36 (39%) patients experienced spinal and femoral neck bone loss, respectively, with mean annual percent Bh ID chang es of -2.0% and -1.5%, respectively. NTx, a bone resorption marker, inverse ly correlated with spinal BMD rate of change (r = -0.4, p < 0.05). Using qu artiles analysis, patients with the highest NTx (Q4) experienced the greate st decrease in spine BMD compared with patients with the lowest NTx (Q1). CONCLUSIONS: Spine and femoral neck bone loss continues over time in mon th an one-third of IBD patients. Increased NTx level predicts spinal bone loss in IBD patients. (Am J Gastroenterol 2000,95:699-704. (C) 2000 by Am. Coll . of Gastroenterology).