Thyroglobulin (Tg) is a glycoprotein of high molecular weight (660kDa) localized within the colloid of the thyroid follicle. It palys an essential role in the storage of iodine and acts as substratum for the synthesis of iodinated thyroid hormones thyroxine (T4) and 3,5,3 – triiodothyronine (T3).
Tg is one out of three major thyroid autoantigens (besides thyroid peroxidase (TPO) and the TSH-receptor). Detecting autoantibodies to Tg today is an established tool for diagnosing chronic autoimmune thyroiditis as well as for the differential diagnosis of hypothyroidism including its subclinical or latent type.
Autoantibodies to Tg and TPO are important for ruling out autoimmune thyroid diseases, as over 98% of thyroiditis patients display autoantibodies to either one or both of these antigens. Anti-Tg is found in 30% of patients with Graves disease and 85% of patients with Hashimoto’s thyroiditis. Thus negative testing for anti-Tg and anti-TPO can virtually exclude a diagnosis of thyroiditis. These autoantibodies do also occur in patients with adenocarcinoma of the thyroid or hyperthyroidism.
Approximately 10% of healthy individuals have anti-Tg antibodies at low levels. A follow-up to a 20-year community study in England concluded that a primary risk factor to future autoimmune thyroid disfunction was a positive thyroid autoantibody test. Therefore these antibodies have a predictive value, too.
Immunoenzymatic method for the quantitative determination of IgG class antibodies against Thyroglobulin (Tg) in human serum, using a disposable device applied on the Chorus and Chorus TRIO instruments. The test is based on the ELISA principle (Enzyme Linked ImmunoSorbent Assay) which uses the reaction between the antibodies present in the tested sample and the immobilized antigen bound to solid phases.The immunoglobulins bind to the antigen through incubation with diluted human serum.The disposable devices contain all the reagents to perform the test when applied on the Chorus instruments. The results are expressed in International Units (IU/ml) calculated in reference to WHO 65/093.