Celiac Disease in Type 1 Diabetes Ups Risk of Thyroid Disorder

Tara Haelle

December 30, 2015

For patients with type 1 diabetes, having celiac disease increases the risk of developing autoimmune thyroid disease at some point in life, according to a new cohort study published online December 17 in Diabetes Care.

"Given the increased long-term risk of developing autoimmune thyroid disease in patients with both celiac disease and type 1 diabetes, our work would support screening for autoimmune thyroid disease in this high-risk group of patients," write Dr Matthew Kurien, of the University of Sheffield, United Kingdom, and colleagues.

"A pragmatic approach that we would advocate for screening in these high-risk patients would be to measure thyroid peroxidase antibody and thyroid-stimulating hormone at baseline and then annually thereafter."

The authors also draw attention to quality-of-life concerns associated with these diagnoses.

"Given the previously recognized reduction in quality of life in patients with celiac disease, clinicians should be mindful that patients with celiac disease, autoimmune thyroid disease, and type 1 diabetes have a higher potential risk of psychological problems, which should trigger early referral to healthcare professionals with relevant expertise if concerns are identified," they write.

Lack of Consensus on Which Thyroid Function Tests to Do

Researchers combed the Swedish National Patient Register for those diagnosed with type 1 diabetes up to age 30 years between 1964 and 2009. They then searched for all patients with celiac disease based on small intestinal biopsy reports showing villous atrophy (Marsh histopathology grade III) at any of Sweden's pathology departments between 1969 and 2008.

From these cohorts, the authors identified 947 patients with both type 1 diabetes and celiac disease. The median age of diagnosis was 9 years for type 1 diabetes and 12 years for celiac disease, and patients were tracked for a median of 13 years.

Then authors matched these patients to 4584 controls who had type 1 diabetes but not celiac disease to calculate their risk of autoimmune thyroid disease — a diagnosis of hyper- or hypothyreosis — over 8890 person-years of follow-up.

Although 54 of the patients with type 1 diabetes and celiac disease would typically be expected to have autoimmune thyroid disease, 90 patients did.

The incidence of autoimmune thyroid disease among patients with type 1 diabetes and celiac disease was 1012 per 100,000 person-years, compared with 607 per 100,000 person-years in the control group.

In terms of absolute risk, 10.8% of patients with type 1 diabetes and celiac disease had autoimmune thyroid disease at some point in life, compared with 7.2% of those with type 1 diabetes alone.

After accounting for sex, age, and range of years diagnosed with diabetes, patients with type 1 diabetes and celiac disease were almost 70% more likely to have autoimmune thyroid disease (hazard ratio [HR], 1.67; P < .001).

More specifically, having celiac disease increased the risk by 66% for hypothyreosis and by 72% for hyperthyreosis. And among those diagnosed with celiac disease at least 10 years earlier, the risk for thyroid disease more than doubled (HR, 2.22; P < .001).

"Currently, there is a lack of consensus from major endocrine and diabetes societies' guidelines as to which thyroid-function tests should be performed and as to when screening should be undertaken," the authors write.

"Although uncertainty exists regarding the merits and the cost-effectiveness of these differing screening strategies, findings from our work suggest that patients with both celiac disease and type 1 diabetes are at particularly high risk of developing autoimmune thyroid disease."

The authors note that the lowest risk for thyroid disease occurred among those diagnosed with type 1 diabetes in childhood.

However, autoimmune thyroid disease is most strongly associated with those age 45 to 50 years, so they suggest that it's likely they didn't see the highest rates because of the median ages of those surveyed.

And, "as our median follow-up was 13 years, this may have been insufficient time for those diagnosed at an early age to have reached the typical age of autoimmune thyroid disease."

The research was funded by the Swedish Society of Medicine, Swedish Research Council, and Swedish Celiac Society. The authors reported no relevant financial relationships.

Diabetes Care. Published online December 17, 2015. Abstract

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