Background: Coeliac disease may be associated with a wide variety of diseases of known or suspected immunological aetiology.
Objective: To screen for both (a) the prevalence of coeliac disease in adults with autoimmune thyroid diseases, and (b) thyroid impairment among adults with coeliac disease, as compared to sex- and age-matched controls.
Design: Prospective cohort study.
Setting: University teaching hospital.
Patients: A total of 152 consecutive adults with autoimmune thyroid diseases, 185 consecutive coeliac disease patients (53 newly diagnosed and 132 already on a gluten-free diet) and 170 sex- and age-matched controls.
Methods: Screening for coeliac disease was done by means of IgA anti-endomysium antibodies, detected by indirect immunofluorescence on monkey oesophagus. Patients with positive sera underwent duodenal biopsy for diagnostic confirmation. Thyroid function was assessed by measuring the levels of serum thyroid-stimulating hormone, free T3, free T4, thyroperoxidase and thyroid microsome antibodies. Autoimmune thyroid diseases were classified according to the American Thyroid Association guidelines.
Results: Anti-endomysium antibodies were positive in five of 152 autoimmune thyroid disease patients (3.3%) and coeliac disease was histologically confirmed in all: this prevalence is 10-fold higher than expected. Only one patient presented with gastrointestinal complaints, but iron deficiency was found in three and alterations at bone mineralometry in all. The overall prevalence of autoimmune thyroid diseases was significantly higher (38/185, 20.5%) in coeliac patients than in controls (19/170, 11.2%). The prevalence of both hypo- and hyperthyroidism was not different from that of controls, while the prevalence of autoimmune thyroid disease with euthyroidism was 13% in patients and 4.7% in controls.
Conclusions: The association of coeliac disease with autoimmune thyroid disease is not surprising as they share common immunopathogenetic mechanisms. It is advisable to screen autoimmune thyroid disease patients for coeliac disease as there is an increased risk for gluten intolerance. In contrast, thyroid function assessment in coeliac disease patients is probably less justified, although the need for a strict clinical follow-up of those patients with euthyroidism and autoimmune thyroid disease, who could develop overt thyroid impairment, remains an open question.