When Type 1 Diabetes Comes With Thyroid Disease: What Families Should Know

Autoimmune polyglandular syndrome type 3a (APS-3a) is a medical term for when someone has both Type 1 diabetes and autoimmune thyroid disease. It's called a 'syndrome' because the two conditions occur together more often than by chance alone. Both diseases happen when the immune system mistakenly attacks the body's own tissues—in this case, the insulin-producing cells in the pancreas and the thyroid gland.

This is different from having Type 1 diabetes plus an unrelated health condition. APS-3a reflects an underlying tendency toward autoimmunity that affects multiple glands and organs.

A large study tracking 439 children with Type 1 diabetes over 16 years found that about 23.5% of them also developed autoimmune thyroid disease. This means roughly 1 in 4 children with Type 1 diabetes may eventually be diagnosed with a thyroid autoimmune condition.

The study also found that girls are more likely than boys to have both conditions (54.4% of cases were girls). In nearly half of all cases, children received both diagnoses around the same time, often at the moment Type 1 diabetes was first identified.

Among children with Type 1 diabetes who develop thyroid disease, Hashimoto's thyroiditis is far more common, occurring in 96% of cases. Hashimoto's is a condition where the immune system attacks the thyroid, gradually reducing its ability to produce thyroid hormone.

Graves' disease, a different type of autoimmune thyroid disease where the immune system overstimulates the thyroid, represented only 4% of cases in this study. This means if your child develops thyroid disease alongside Type 1 diabetes, Hashimoto's is much more likely.

While APS-3a (Type 1 diabetes plus thyroid disease) is the most common combination, some children in the study developed additional autoimmune conditions. These included celiac disease, autoimmune hepatitis, atrophic gastritis, vitiligo, psoriasis, and Sjögren's syndrome.

The unpredictable nature of these overlapping autoimmune conditions emphasizes why families need regular monitoring. This doesn't mean your child will develop these other conditions—only that the possibility exists and warrants ongoing attention.

Because thyroid disease is common in children with Type 1 diabetes, regular thyroid screening is part of standard Type 1 diabetes care. Your child's healthcare team typically checks thyroid function through blood tests at diagnosis and then periodically during follow-up visits.

If your child has both Type 1 diabetes and thyroid disease, lifelong monitoring remains important. This helps catch any new autoimmune conditions early and ensures both conditions are managed well. Talk with your healthcare provider about the right screening schedule for your child.

Source: Diabetes & metabolism. Evidence type: PubMed indexed literature. Type1Cure is an information and intelligence hub, not a medical advice service. This article summarizes published research and does not provide diagnosis, treatment, or personal medical guidance. Always talk to your own care team before changing anything about your Type 1 diabetes management.