Thyroid Antibodies

Thyroid antibodies are proteins made by your immune system that mistakenly target your thyroid gland. Having elevated levels means your immune system may be attacking your thyroid, which can affect how well it works over time. Different types of thyroid antibodies are linked to different conditions — some are associated with an underactive thyroid (Hashimoto's disease) and others with an overactive thyroid (Graves' disease). A positive result does not always mean you currently have symptoms, but it does mean your doctor may want to monitor your thyroid function more closely. These results are most meaningful when reviewed together with other thyroid blood tests.

When elevated: Elevated thyroid antibodies suggest active autoimmune thyroid disease, increased risk of progression to overt hypothyroidism or hyperthyroidism, and potential need for closer thyroid function monitoring. In pregnancy, high levels warrant enhanced surveillance for maternal and fetal thyroid complications. When low: Low or undetectable thyroid antibody levels make autoimmune thyroid disease less likely as a cause of thyroid dysfunction, though seronegative autoimmune thyroiditis can occur. Low levels in monitored patients may reflect disease remission or treatment response.

Thyroid autoimmunity can impair metabolic rate, energy availability, and recovery—potentially affecting endurance, strength gains, and training tolerance. Athletes with undiagnosed autoimmune thyroid disease may experience persistent fatigue, unexplained performance drops, or difficulty losing weight despite training; screening is useful if these symptoms appear alongside family history of thyroid disease or other autoimmune conditions.