Bone Mineral Density, Type 1 Diabetes, and Celiac Disease

Correspondence in Diabetes Care has highlighted the importance of two secondary causes of reduced bone mineral density (BMD) in type 1 diabetes, namely thyrotoxicosis and primary hyperparathyroidism (1,2). We describe another secondary cause of reduced BMD. Celiac disease is associated with reduced BMD and reversible secondary osteoporosis in the general population (3,4). Celiac disease is not uncommon in type 1 diabetes, with a prevalence of 1–7.8% (5). The association between celiac disease, type 1 diabetes, and osteopenia has been discussed in Diabetes Care (6), but the impact of celiac disease on BMD in type 1 diabetes has not been quantified.

We undertook a population-based study of BMD in 99 women with type 1 diabetes using dual-energy X-ray absorptiometry, as previously described (7). Although multiple clinical determinants of BMD were assessed, no subject had diagnosed celiac disease, and we did not undertake any screening tests for undiagnosed celiac disease at the time of the initial study. After the completion of the study, women with a reduced BMD (Z score of –1 or less) were investigated for secondary causes of osteopenia, and four women were found to have celiac disease. Ethics committee approval was then obtained to screen the remaining women for celiac disease using the IgA endomysial antibody (EMA) serological test.

A total of 10 of the 99 subjects were EMA positive, and all 10 subjects had features of celiac disease on small bowel biopsy. Seven subjects had minor gastrointestinal symptoms that resolved after the introduction of a gluten-free diet. The remaining three subjects were asymptomatic. The 10 women with a new diagnosis of celiac disease were younger than the 89 women without celiac disease (mean age 37 and 43 years, respectively); therefore, BMD was adjusted for age. The mean age-adjusted (standard deviation) Z score at the lumbar spine was −0.98 for the 10 subjects with celiac disease, compared with −0.12 for the 89 subjects with diabetes alone (P = 0.03). The corresponding mean Z scores at the femoral neck were −0.72 and −0.06, respectively (P = 0.11). The Z score for all 99 women studied was −0.21 at the lumbar spine and –0.12 at the femoral neck (7), thus the impact of removing the 10 subjects with celiac disease from the calculation of the study population’s mean BMD was negligible.

The above results from women with type 1 diabetes are consistent with the previously described finding in the general population, which shows an association between untreated celiac disease and reduced BMD. Celiac disease should be considered as a possible secondary cause of osteopenia in type 1 diabetic patients found to have a reduced BMD. We recommend that future studies examining determinants of osteopenia in type 1 diabetes include a sceening test for celiac disease. The presence of celiac disease had minimal impact on the mean BMD of the population studied, thus the results do not support the hypothesis that celiac disease is the principal cause of the reduced BMD described in association with type 1 diabetes.