Chapter 30 - Autoimmune thyroid diseases

Autoimmune thyroid diseases include chronic autoimmune thyroiditis (CAT) with its variants and Graves’ disease (GD). Both disorders have a genetic predisposition, but existential and environmental factors play a relevant role in their development. There is a spectrum of functional abnormalities: while GD is characterized by hyperthyroidism, CAT may be associated with a normal thyroid function, but with time evolves in the majority of cases to hypothyroidism. Overt dysfunction is usually preceded by a subclinical phase, during which diagnosis is made on serological and ultrasonographic grounds. Circulating antithyroglobulin, antithyroperoxidase, and antithyrotropin receptor autoantibodies are biomarkers of the disease. GD and CAT may coexist in the same individual, explaining the possible swinging from hyperthyroidism to hypothyroidism, or, less frequently, from hypothyroidism to hyperthyroidism. Familial clustering of autoimmune thyroid disorders is frequently observed, and some members of the family may be affected by GD, while others have CAT with or without hypothyroidism.