Approximately 2-5 percent of people with type 1 diabetes have an underactive thyroid and are called hypothyroid. Up to 20 percent of people with type 1 diabetes have positive antithyroid antibodies that can be measured in the blood. Many people with antithyroid antibodies will go on to develop an autoimmune underactive thyroid called Hashimoto's thyoiditis.
It is suggested that children and adolescents with type 1 diabetes should be screened for autoimmune thyroiditis. If thyroid-stimulating hormone (TSH) levels are normal, it is suggested that screening should take place every 1-2 years as they develop an undeactive thyroid in the future.