IgG4 antibodies in autoimmune thyroid disease

Thyroiditis (inflammation of the thyroid gland) is a condition that can be triggered by infectious diseases, pregnancy, radiation, and toxins. Thyroiditis is often the result of attacking antibodies and inflammation chemicals produced by the immune system. Our bodies must be able to differentiate between “self” and “non-self” cells in order to fight off infections from bacteria, viruses, and parasites. The immune system makes antibodies to accomplish this task. The structures of these antibodies are specifically designed to bind to certain molecules, ideally to those associated with infectious organisms. Autoimmune diseases occur when the immune system makes a mistake, producing autoantibodies that target normal tissues in the body. We do not fully understand why these mistakes occur in nature, but it is thought that there may be a genetic component at play. Studies have shown that individuals with high levels of two particular autoantibodies most likely inherited the disease from their parents. The targets of these antibodies are thyroglobulin (which is used by the thyroid gland to produce thyroid hormones) and thyroperoxidase (which liberates iodine for use by the thyroid gland), are both vital proteins for thyroid function. In these patients, the autoantibodies are of a specific type of immunoglobulin called IgG4. High levels of IgG4, thyroglobulin and thyroperoxidase autoantibodies may indicate the occurrence of a specific (more severe) form of thyroiditis that is passed along genetically in families. If this is the case, testing for these proteins may become a practical and valuable tool in identifying this condition at an earlier stage, resulting in better treatment outcomes.

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