A clinically meaningful impairment of bone mass secondary to malabsorption is frequent in untreated celiac disease. In adult patients, a rigorous gluten-free diet (GFD) significantly improves, but does not always normalize, bone mineral density (BMD). The reason for this marginal response is unclear. Accordingly, we evaluated the role of both local and systemic factors for bone loss in celiac patients on long-term GFD.
In a prospective cohort, 22 patients with low lumbar and/or femoral BMD and 22 with normal BMD underwent bone and mineral metabolism evaluation: we tested calcium, phosphate, parathyroid hormone, and vitamin D; telopeptide of type I collagen, a bone resorption index; propeptide of type I procollagen, a bone neoformation index; receptor antagonist of NF-kB ligand, an osteoclast-stimulating factor; osteoprotegerin (OPG), a decoy receptor for RANKL. Sunlight exposure and physical exercise were measured.
Patients with bone loss showed prevalently osteopenia, severe osteoporosis was rare. In comparison with normal BMD patients, they showed higher serum OPG, telopeptide, and lower serum propeptide, suggesting an increased bone turnover. Lumbar T-score was negatively correlated with OPG, telopeptide and RANKL and positively with propeptide. Propeptide was negatively correlated with OPG and telopeptide. OPG was positively correlated with telopeptide.
The persistent activation of inflammation should be considered the main pathophysiological mechanism for bone defect in celiac disease patients with bone loss on long-term GFD. High levels of OPG, an attempt at protective mechanism, and low levels of propeptide of type I procollagen, reflecting an insufficient matrix production, characterize this subgroup of patients.