Sodium iodide symporter: its biology, clinical relevance, and potential role in the pathophysiology of autoimmune thyroid disease

As the thyroidal membrane protein that mediates iodide transport into thyroidal follicular cells, sodium iodide symporter plays a key role in thyroid pathophysiology and allows effective use of radioiodine for diagnosis and therapy of thyroid cancer. Because of the critical role sodium iodide symporter plays in thyroid function, its potential role as a novel thyroid autoantigen in the pathogenesis of autoimmune thyroid disease has become the focus of many studies. Recent reports involving large series of patient samples and specific and quantitative binding assays were unable to confirm early, promising data that suggested a pathogenic role of sodium iodide symporter in autoimmune thyroid disease. On the other hand, although further studies are needed to determine the clinical importance of sodium iodide symporter as a thyroidal autoantigen, sodium iodide symporter expression detected in mammary glands may have important diagnostic and therapeutic implications in breast cancer. One of the most exciting and promising chapters of sodium iodide symporter gene-based research since its cloning in 1996 is the characterization and application of sodium iodide symporter as a novel therapeutic gene for cytoreductive gene therapy based on targeted sodium iodide symporter gene transfer followed by radioiodine therapy for nonthyroid malignancies.