Younger Age at Onset of Type 1 Diabetes in Concordant Sibling Pairs Is Associated With Increased Risk for Autoimmune Thyroid Disease

Abstract

Individuals with type 1 diabetes are at increased risk for the development of additional autoimmune disorders compared with the general population (1–11). Autoimmune thyroiditis (AIT) and celiac disease are relatively common among patients with type 1 diabetes, with prevalence rates of ∼17 and 6%, respectively (4). We sought to examine the relationship between age at onset of type 1 diabetes and prevalence of additional autoimmune disorders in a sample of sibling pairs concordant for type 1 diabetes. Sibling pairs concordant for type 1 diabetes who visited the Joslin Diabetes Center’s Pediatric, Adolescent, and Young Adult Section between June 2002 and March 2005 were identified via a search of the electronic patient database. All identified patients were insulin dependent since diagnosis and showed no evidence of insulin resistance. Monozygotic twin pairs were excluded from the study. Charts were analyzed for evidence of additional autoimmune disorders. The institutional review board approved the study protocol. Sibling pairs were classified according to age at type 1 diabetes diagnosis. Group 1 was composed of pairs in which both proband and sibling were diagnosed at <10 years of age. Group 2 was composed of all other pairs (i.e., at least one sibling diagnosed at 10–18 years). Screening for thyroid dysfunction was performed by obtaining thyroxine (T4 and T3RU) and/or serum thyrotropin (TSH). At least one screening was performed every 2 years in 90% of the patients. Screening for celiac disease was obtained on any patient with symptoms …