Endocrine Abstracts

Background: The association of autoimmune thyroiditis (AIT) with nonendocrine autoimmune disorders has been reputed for long time as a variant of type 2 polyglandular autoimmune syndrome (PAS2). Nowadays, it is framed in the picture of polyautoimmunity and its relevance is owed to its prevalence, far higher than PAS 2, and its expanding galaxy. Systematic studies on this field are rather scanty and mostly based only on the presence of circulating antibodies. Our study has been designed, over the last ten years, to diagnose all the autoimmune disorders sequentially diagnosed in patients with already known lymphocytic thyroiditis.

Methods: In a cohort of 9,415 consecutive outpatients, AIT was diagnosed in 2884 (30.6%). If suspected on clinical and/or immunological ground, the presence of further autoimmune disorders was ascertained on the basis of Consensus or Guidelines specific for each disease. Histological confirmation was obtained in all gastrointestinal disorders.

Results: The presence of AIT in a frame of poly-autoimmunity has been observed in 358 patients (12.8%)(315W/43M; median age=39 years). Of these, 34 patients (10.5%) had more than one autoimmune disorder associated with AIT. The most frequent associated disease was chronic atrophic gastritis (CAG) (30.4%), followed by non-segmental vitiligo (19.9%), celiac disease (11,8%), and multiple sclerosis (7.2%). The juvenile form (<30 yrs) accounted for 14.5% of the whole sample and was characterized by a higher frequency of celiac disease (44.2%) associated with thyroiditis, followed by vitiligo (13.4%), while CAG was less observed (7.7%). These poly-autoimmune patients showed peculiar clinical features. In fact, thyroxine malabsorption was higher than in patients with isolated thyroid diseases (34.6 vs 8.1%; P < 0.0001;OR=5.953). Unexplained anemia was also significantly higher in euthyroid patients with polyautoimmunity (23.2 vs 6.8%; P < 0.0001 OR=4.105) than in euthyroid patients with isolated AIT. Also, recurrent pregnancy loss was also clearly increased (6.9% vs 1.7%; P < 0.0001; OR=4.06) in poly-autoimmune patients as compared with isolated AIT.

Conclusions: Additional autoimmune disorders were diagnosed in 1/8 patients with AIT and 1/10 of them was younger than 30 years. Atrophic gastritis, vitiligo and celiac diseases were the most frequent autoimmune disorders associated with AIT, with a clear age-related prevalence. The presence of thyroxine malabsorption, chronic unexplained anemia and recurrent pregnancy loss in patients with AIT are clinical features of poly-autoimmunity and should prompt further diagnostic workup for associated autoimmune disorders.