Anti-thyroglobulin (ATG) antibodies
Why this test?
To detect autoimmune damage to the thyroid gland (mainly diffuse toxic goiter and Hashimoto's thyroiditis). To determine risk groups for the development of thyroid diseases among children born to mothers with pathology of endocrine organs. For follow-up in the postoperative period of patients with thyroid cancer to rule out recurrence and metastases (together with thyroglobulin analysis).
In what cases is it prescribed?
If thyroid disease is suspected, indicated by a change in its size and structure, ophthalmopathy, weight loss, tachycardia, increased fatigue. When prescribing thyroglobulin, to monitor the condition of patients after removal of a thyroid tumor. In case of systemic autoimmune diseases (to determine the risk of damage to the thyroid gland). In case of violation of the female reproductive function and suspicion of its connection with the presence of autoantibodies.
Thyroglobulin is a glycopeptide, a precursor of triiodothyronine (T3) and thyroxine (T4). It is produced only by the cells of the thyroid gland and accumulates in its follicles in the form of a colloid. When hormones are secreted, a small amount of thyroglobulin enters the blood. For unknown reasons, it can become an autoantigen, and in response, the body produces antibodies to it, which causes inflammation of the thyroid gland.
AT-TH can block thyroglobulin, disrupting the normal synthesis of thyroid hormones and causing hypothyroidism, or, on the contrary, excessively stimulate the gland, causing its hyperfunction. Antibodies to thyroglobulin simultaneously interact with the components of the connective tissue of the eyeball, eye muscles and the enzyme acetylcholinesterase.
It is possible that an autoimmune reaction is the cause of changes in the tissues of the eyeball in thyrotoxic ophthalmopathy. AT-TG is detected in 40-70% of patients with chronic thyroiditis, in 70% of patients with hypothyroidism, in 40% with diffuse toxic goiter and in a small number of patients with other autoimmune pathologies, including pernicious anemia. Although the level of antibodies is slightly elevated in healthy people, especially elderly women.
The test is mainly useful in confirming the patient's diagnosis of "diffuse toxic goiter" and/or "hypothyroidism due to autoimmune thyroiditis". In addition, it is valuable in the differential diagnosis of basal disease and toxic nodular goiter.
Despite the fact that AT-TG are less often detected in blood serum than thyroid microsomal antibodies (antibodies to peroxidase), in patients with autoimmune diseases of the thyroid gland, the results of this analysis are also important to confirm the diagnosis.
If a pregnant woman has autoimmune thyroid disease or any other autoimmune pathology, a test for one or more thyroid antibodies should be prescribed at the beginning of pregnancy and shortly before delivery to predict the risk of thyroid disease in the newborn.