The study was aimed to evaluate osteoporosis prevalence in a group of Tunisian patients with inflammatory bowel disease (IBD), to determine its risk factors, and to describe its mechanisms.

We included 67 IBD patients, 43 patients with Crohn's disease (CD) and 24 with ulcerative colitis (UC). Bone mineral density was measured at the lumbar spine and left femoral neck by dual-energy X-ray absorptiometry. We used T score to express bone loss (osteopenia: – 2.5 SD ≪ T ≪ – 1 SD, osteoporosis: T ≪ – 2.5 SD). Biochemical assessment of serum total alkaline phosphatases, osteocalcin, parathyroid hormone, vitamin D, interleukin-6, and urinary degradation products of C-telopeptide of type I collagen (CrossLaps), was also performed.

Prevalence of femoral osteoporosis was 31.8% and 13% in CD and UC patients, respectively and that of lumbar osteoporosis 40.9% and 8.7%, respectively. Femoral neck osteoporosis tended to be more frequent in CD (odds-ratios-OR = 3.13 [95% CI: 0.79-12.5], P = 0.09), in females (OR = 2.20 [0.69-6.72], P = 0,18) and in patients with active disease (OR = 3.13 [0.94-10.00], P = 0.06). Lumbar osteoporosis was significantly associated with CD (OR = 7.14 [1.52-33.33], P ≪ 0.01). Low body mass index ≪ 20 kg/m², disease course > 2 years and active disease tended to be associated with lumbar osteoporosis; the ORs were respectively 4.87 [0.9225.80] (P = 0.06), 4.21 [0.87-20.57] (P = 0.06), and 2.33 [0.78-6.67] (P = 0.13). No association was found with cumulated dose of steroids even when considering only CD. Patients with osteoporosis showed significant increased CrossLaps and interleukin-6 levels that indicate both high bone resorption and inflammatory activity.

Osteoporosis is frequent in IBD patients, especially in CD patients. Female gender, malnutrition (body mass index ≪ 20 kg/m²), disease course (> 2 years) and active disease would be risk factors of bone mineral loss in IBD. Osteoporosis is associated with enhanced bone resorption, that seems be linked to excessive intestinal inflammation.