Thyroglobulin and thyroglobulin antibodies measurement and interferences

Abstract

Thyroglobulin, an approximately 670-kDa glycopeptide, is the major protein product of thyroid follicular cells; its rate of synthesis is increased by thyrotropin (TSH). After synthesis, it is modified by the attachment of iodine to selected tyrosine residues, which undergo rearrangement to form iodothyronines, particularly thyroxine (T4) and, to a lesser extent, thysonine (T3). Other modifications of thyroglobulin also occur, including glycation and sulfation (1). The degree of TSH stimulation affects the extent of branching of carbohydrate side chains (2). There is variable processing of thyroglobulin, creating a family of proteins with different molecular structures around a common core peptide backbone. Interestingly, there is less variability in thyroglobulin structure in thyroid cancer than in other thyroid diseases (3). Reduced iodine content in thyroglobulin exists in patients with thyroid malignancy (4), which can lead to different recognition by monoclonal antibodies (5). This structural heterogeneity creates a challenge for thyroglobulin immunoassays, and results often differ significantly when using different thyroglobulin methods (6). © 2006 Humana Press Inc.