People with celiac disease, hyperthyroidism, or hypothyroidism are significantly more likely to develop type 1 diabetes than those without these autoimmune conditions, according to a new study of more than 1.2 million individuals. The risk was highest in children and adolescents and remained elevated regardless of family history.

The analysis used U.S. health insurance claims data from 2017 to 2023. Individuals with any of the three autoimmune diseases were matched 1:1 with controls without these conditions. Participants were followed for a median of about 2 years to assess new cases of type 1 diabetes.

Among 47,099 individuals with celiac disease, 0.14% developed type 1 diabetes compared with 0.06% of controls. In the hyperthyroidism group (n = 164,830), 0.17% developed type 1 diabetes versus 0.06% of controls. In the hypothyroidism group (n = 980,477), 0.18% developed type 1 diabetes compared with 0.08% of controls.

The researchers found the following hazard ratios:

• Celiac disease was associated with a 2.54-fold increased risk (hazard ratio [HR] = 2.54).

• Hyperthyroidism carried a 2.98-fold increased risk following adjustment (HR = 2.98).

• Hypothyroidism was linked to a 2.41-fold increased risk (HR = 2.41).

Risk was greater among those under 18 years of age:

• Celiac disease: 3-fold higher risk.

• Hyperthyroidism: 8-fold higher risk.

• Hypothyroidism: 3.5-fold higher risk.

Among all groups, individuals with autoimmune disease developed type 1 diabetes more quickly than controls. Risk remained elevated even among those newly diagnosed with the autoimmune condition during the study period.

A sensitivity analysis, which defined type 1 diabetes by both diagnostic code and basal insulin use, confirmed higher risk among individuals with celiac disease and hyperthyroidism.

The increased risk also applied to individuals without a family history of type 1 diabetes. While screening guidelines often emphasize genetic risk, the findings suggest that people with celiac or thyroid disease may also benefit from early screening.

Unlike prior studies focused on children, this research included both pediatric and adult populations, offering broader insight into the association between autoimmune conditions and type 1 diabetes.

The researchers noted limitations, including reliance on diagnostic codes, possible misclassification, and incomplete patient histories. Despite these, the results consistently showed a strong association between autoimmune thyroid or gastrointestinal disease and the later development of type 1 diabetes.

The findings may help inform future screening and monitoring strategies for individuals at increased risk.

Full disclosures can be found in the published study.

Source: Diabetes, Obesity and Metabolism