The Autobio T4 assay is designed for the quantitative determination of Thyroxine (T4) concentration in human serum.
Thyroxine or 3, 5, 3', 5'-tetraiodo-L-thyronine (T4) is the major hormone produced by the thyroid gland. It has a molecular weight of 777 daltons and is synthesized by iodination of tyrosine residues on thyroglobulin. Proteolytic cleavage of follicular thyroglobulin releases T4 into the bloodstream. Greater than 99% of T4 is reversibly bound to three plasma proteins in blood - thyroxine binding globulin (TBG) binds 70%, thyroxine binding pre-albumin (TBPA) binds 20%, and albumin binds 10%. Approximately 0.03% of T4 is in the free, unbound state in blood at any time.
Diseases effecting thyroid function may present a wide array of confusing symptoms. Measurement of total T4 by immunoassay is the most reliable and convenient screening test available to determine the presence of thyroid disorders in patients. Increased levels of T4 have been found in hyper-thyroidism due to Grave's disease and Plummer's disease and in acute and subacute thyroiditis. Low levels of T4 have been associated with congenital hypothyroidism, myxedema, chronic thryoiditis (Hashimoto’s disease), and with some genetic abnormalities.
