The thyroid cells are typical protein-secreting glandular cells. Theendoplasmic reticulum and Golgi apparatus synthesize and secrete into thefollicles a large glycoprotein molecule called thyroglobulin (Tg), with amolecular weight of about 335,000.Each molecule of thyroglobulin contains about 70 tyrosine amino acids, andthey are the major substrates that combine with iodine to form the thyroidhormones. Thus, the thyroid hormones are formed within the thyroglobulinmolecule. (1)In most clinical situation, thyroglobulin concentrations are determined bythree factors:1. Thyroid cell mass.2. Physical damage to thyroid (by biopsy, surgery, haemorrhage, radioactiveiodine [RAI], external irradiation, or inflammation), with thyroiditis being themost common clinically encountered effect.3. Activation of Thyroid Stimulating Hormone (TSH) receptors by TSH, orthyroid stimulating antibody (TSAb)/thyroid stimulating immunoglobulin (TSI). (2)Serum thyroglobulin measurement has greatly facilitated the clinicalmanagement of patients with differentiated thyroid cancer and a variety ofother thyroid disorders. Thyroglobulin autoantibodies remain a significantobstacle to the clinical use of thyroglobulin measurements. The interpretationof any given thyroglobulin value requires the careful assessment of allclinical and laboratory data available to the clinician.