Clustering of additional autoimmunity behaves differently in Hashimoto's patients compared with Graves' patients.

OBJECTIVE: It is unclear whether Hashimoto's thyroiditis and Graves' disease (often referred to as autoimmune thyroid disease, AITD) cluster to the same extent with other autoimmune disorders.
METHODS: We assessed adrenal, β-cell, celiac and gastric antibodies in a cohort of 523 adult patients with Graves' disease and 359 patients with Hashimoto's disease and compared their clustering.
RESULTS: Adrenal autoimmunity associated more often with Hashimoto's disease (9.0%) than with Graves' disease (3.3%, P=0.001). β-cell autoimmunity was seen more frequently in Hashimoto's disease (25.4%) than in Graves' disease (15.6%, P=0.001) patients. We found low prevalences of celiac autoimmunity (1.2% for Graves' and 1.2% for Hashimoto's disease). Celiac and gastric autoimmunity were not statistically different in Hashimoto's and Graves' disease patients. Although gastric autoimmunity itself was equally prevalent (around 20%), Hashimoto's disease often showed significantly more clustering of adrenal autoimmunity with gastric autoimmunity (5.3%) than Graves' disease (1.2%, P=0.001). Similarly, clustering of adrenal autoimmunity was seen with β-cell autoimmunity in Hashimoto's patients (3.2%), while such clustering was much less encountered in 359 Graves' patients (0.9%, P=0.029).
CONCLUSION: In conclusion, Hashimoto's disease shows a markedly higher clustering of additional autoimmunity, especially with adrenal and β-cell autoimmunity. Combined clustering of gastric and adrenal autoimmunity and combined clustering of adrenal and β-cell autoimmunity were both seen more often in Hashimoto's patients. Clustering with celiac disease appears to be low. These findings indicate that Hashimoto's and Graves' disease differ in their clinical expression regarding additional autoimmunity, which argues against the indiscriminate use of AITD as an entity.