Data from the population-based HUNT Study in Norway revealed an association between autoimmune diabetes and the prevalence of hypothyroidism and hyperthyroidism. However, researchers found no association between type 2 diabetes and thyroid dysfunction.
Previous studies have found associations between autoimmune diabetes and autoimmune thyroid disease, as they share some of the same susceptibility genotypes that are involved in immune regulation. Even so, evidence linking type 2 diabetes with thyroid dysfunction is still limited.
“Our results suggest that people with autoimmune diabetes may be prone to earlier development of hypothyroidism, as their age at diagnosis tended to be lower than among people without diabetes,” the researchers noted in their study, published in the Journal of Clinical Endocrinology and Metabolism. “Alternatively, increased surveillance with autoimmune diabetes may contribute to their earlier diagnosis.”
The HUNT Study included 3 surveys (HUNT1-3) involving self-reported information provided by adults at least 20. Participants underwent clinical examinations and provided blood samples for analysis.
The researchers conducted a cross-sectional population-based study of adults in HUNT2 and HUNT3. They examined the data from 34 235 participants in HUNT2 and 48 809 participants in HUNT3 to analyze associations between autoimmune and type 2 diabetes and thyroid dysfunction.
In HUNT 2, autoimmune diabetes appeared to be linked to thyroid dysfunction. The average age-adjusted prevalence ratio of hypothyroidism in individuals with autoimmune diabetes, when compared with individuals without diabetes, was 1.79 (95% CI, 1.30-2.47) for women and 2.7 (95% CI, 1.76-4.19) for men. The prevalence ratios for hyperthyroidism were 2.12 (95% CI, 1.36-3.32) for women and 2.54 (95% CI, 1.24-5.18) for men.
There was no association between hypothyroidism and type 2 diabetes in HUNT 2.
In HUNT 3, a slight association between type 2 diabetes and higher prevalence of hypothyroidism was noted. The prevalence ratios for hypothyroidism were — 1.24 (95% CI, 1.04-1.47) for women and 1.25 (95% CI, 0.93-1.67) for men.
The prevalence ratio of thyroid peroxidase antibodies (TPOAb) in individuals with autoimmune diabetes compared with those without diabetes was higher among men than women (prevalence ratio, 3.00 [95% CI, 1.54-5.85] vs 1.41 [95% CI, 0.96-2.06], respectively), and the researchers saw no association between TPOAb and type 2 diabetes.
Based on their results, the researchers concluded that the risk for thyroid disease may be particularly high among individuals who are diagnosed with autoimmune diabetes at an early age, but additional research is required for this subgroup.
“The findings support the recommendation of regular follow-up of thyroid function in people with autoimmune diabetes,” the researchers wrote. “On the other hand, our results do not support proposals for increased surveillance of hypothyroidism in people with type 2 diabetes.”