Abnormal bone turnover in long-standing Crohn's disease in remission E. J. SCHOON*, B. G. GEERLING*, I. M. A. VAN DOOREN*, L. J. SCHURGERS  , C. VERMEER  , R.-J. M. BRUMMER* & R. W. STOCKBRU È GGER* *Department of Gastroenterology and Hepatology, University Hospital Maastricht, Maastricht, the Netherlands; and  Department of Biochemistry, University of Maastricht, Maastricht, the Netherlands Accepted for publication 24 January 2001 INTRODUCTION Patients with Crohn's disease are at high risk of developing osteopenia and osteoporosis. 1±5 The patho- genesis and pathophysiology of these conditions in Crohn's disease are still not completely understood. A number of factors are considered to contribute to the reduced bone density. These include: steroid use, malnutrition, vitamin D and calcium de®ciency, immo- bilization, smoking, sex hormone de®ciency, hyperpara- thyroidism, and the in¯ammatory process itself. 6 It has been demonstrated that clinical risk factors are poor diagnostic predictors of actual bone mass. 7 In a large controlled study, low bone mineral density was found in patients with Crohn's disease, but not in those with ulcerative colitis. 8 The pathophysiological process can be clari®ed by studying bone turnover by means of biochemical markers that re¯ect bone turnover in the entire skeleton and have the advantage of being non-invasive, relatively inexpensive and of allowing repeated evalu- ation. 9 Biochemical markers of bone resorption are: serum osteocalcinl total and bone-speci®c alkaline SUMMARY Background: A high prevalence of osteoporosis is found in patients with Crohn's disease. The pathogenesis of this condition seems to be multifactorial and its pathophysiology is still not completely understood. Aim: To elucidate the pathophysiology of osteopenia in quiescent Crohn's disease. Methods: Bone turnover was studied in 26 patients (13 males and 13 females) with long-standing quiescent Crohn's disease and small bowel involvement. Bone mineral density was assessed by dual energy X-ray absorptiometry. Biochemical markers for bone forma- tion (osteocalcin and bone-speci®c alkaline phospha- tase) and for bone resorption (deoxypyridinoline and collagen type I C-terminal crosslinks) were measured. Urinary calcium excretion was determined. Results: Markers for bone formation were signi®cantly lower in patients than in controls (osteocalcin: P  0.027, bone-speci®c alkaline phosphatase: P < 0.001), but both bone resorption markers were not signi®cantly different. Urine calcium excretion was signi®cantly decreased in patients (P  0.002) compared to controls. Bone mineral density of the lumbar spine was signi®- cantly and inversely correlated with bone-speci®c alkaline phosphatase and collagen type I C-terminal crosslinks. Conclusions: Bone turnover in long-standing Crohn's disease in clinical remission is characterized by sup- pressed bone formation and normal bone resorption. Urine calcium excretion is decreased. Hence, interven- tions and therapy should be directed towards the improvement of bone formation. Correspondence to: Dr E. J. Schoon, Department of Gastroenterology and Hepatology, University Hospital Maastricht, PO Box 5800, NL-6202 AZ Maastricht, the Netherlands. E-mail: ESCH@sint.azm nL Aliment Pharmacol Ther 2001; 15: 783±792. Ó 2001 Blackwell Science Ltd 783