Coeliac autoimmunity in type I diabetes mellitus

Abstract

Background and study aims: Coeliac autoimmunity (CA) has a known association with type 1 diabetes mellitus (T1DM) for which screening is routinely recommended but less frequently followed. The impact of CA in T1DM has been variably reported. The aims of this study are as follows: (1) to study the prevalence of CA in patients with T1DM and (2) to study the impact of CA not only on nutritional parameters but also on glycaemic control, endocrine axes and bone health.

Patients and methods: Eighty-six consecutive patients with T1DM were screened for CA using immunoglobulin A (IgA) tissue transglutaminase as a marker (TTG; IgG anti-gliadin in IgA-deficient case). CA positive (CA+) cases were compared with age-matched and sex-matched CA negative (CA-) T1DM cases for anthropometry, glycaemic control (assessed by glycated haemoglobin (HbA1c) and hypoglycaemic/hyperglycaemic episodes), endocrine (thyroid function, cortisol, growth hormone (GH) axis, gonadal axes), haematological (haemoglobin, iron profile and vitamin B12 status) and calcium metabolism parameters and bone densitometry (by dual-energy X-ray absorptiometry (DXA)). Consenting patients with CA also underwent upper gastrointestinal (GI) endoscopy with duodenal biopsy.

Results: Out of 86 patients, 11 (12.75%) screened positive for CA (seven patients underwent duodenal biopsies which were suggestive of Marsh grade III(2), II(3) and I(2) disease). The CA+ T1DM patients were comparable with CA- T1DM in terms of anthropometry. CA+ patients had higher HbA1c (10.7±1.8 vs. 8.4±1.0 (93±19 vs. 68±11 mmol/mol); p<0.01), more hypoglycaemic episodes (five vs. two; p<0.05), higher prevalence of iron and vitamin B12 deficiency, lower insulin-like growth factor-1 (IGF-1) levels and lower bone mineral density (BMD) z-score at total body (-1.91±1.05 vs. -0.63±0.73; p<0.05) and lumbar spine (-1.69±0.92 vs. -0.36±0.93; p<0.05). The incidence of fractures in the past 3years was also more in CA+ patients than in CA- patients (four vs. one; p<0.05).

Conclusion: CA has an important autoimmune association with T1DM. The concomitant presence of CA adversely affects stature, bone health, glycaemic control and iron and B12 levels in T1DM. IgA sufficiency should be ensured before using an IgA-based screening test for CA.

Keywords: Bone mineral density; Coeliac autoimmunity; Coeliac disease; Type 1 diabetes mellitus.