Is Hashimoto's Thyroiditis an Autoimmune Condition?
Yes, Hashimoto's thyroiditis is definitively an autoimmune disease characterized by autoimmune-triggered lymphocytic infiltration and destruction of the thyroid gland. 1, 2, 3
Pathophysiology of Autoimmune Destruction
Hashimoto's thyroiditis represents the most common autoimmune endocrine disorder worldwide, with an annual incidence of 0.3-1.5 per 1000 people and affecting approximately 8% of the general population. 4 The disease is fundamentally autoimmune in nature, involving:
Loss of immunological tolerance leading to autoimmune attack on thyroid tissue through both humoral (antibody-mediated) and cellular (T-cell mediated) immunity. 3, 5
Lymphocytic infiltration, particularly T cells, with follicular destruction serving as the histological hallmark of the condition, ultimately leading to gradual thyroid atrophy and fibrosis. 5
Genetic predisposition involving specific HLA associations (HLA-DR/DQ alleles) that can be either predisposing or protective, combined with environmental triggers such as iodine supply, infections, and stress. 6, 2
Association with Other Autoimmune Conditions
The autoimmune nature of Hashimoto's is further confirmed by its frequent coexistence with other autoimmune disorders, demonstrating shared genetic predisposition and environmental triggers:
Type 1 diabetes mellitus, celiac disease, autoimmune hepatitis, systemic lupus erythematosus (2.2-3%), rheumatoid arthritis (2-4%), and Sjögren syndrome (2.8-7%) commonly occur alongside Hashimoto's thyroiditis. 7, 6
In patients with autoimmune hepatitis, autoimmune thyroid disease is the most common concurrent condition, affecting 10-23% of patients, with Hashimoto's specifically accounting for 10.2-14.1% of all concomitant autoimmune diseases. 8
Approximately 20-30% of patients with Hashimoto's have associated organ-specific or systemic autoimmune disorders. 5
Clinical Implications
Screening for additional autoimmune conditions is recommended in patients with Hashimoto's thyroiditis, particularly for the most common associations, with extended diagnostic screening conducted both at diagnosis and at regular intervals during follow-up. 7
Family history should be carefully evaluated as first-degree relatives of Hashimoto's patients have an increased risk of developing autoimmune diseases, reflecting the genetic component of autoimmune susceptibility. 7