[The sodium-iodide-symporter (NIS): function, regulation and clinical importance].

Cloning, functional characterisation, and diagnostic proof of the expression of sodium-iodide-symporter (NIS) in the thyroid are essential steps for a better understanding of function and regulation of thyroid hormone synthesis, which is limited by the availability of the trace element iodide. The physiological or pharmacological modulation of NIS function can now be used for a rational functional diagnosis and therapy of thyroid diseases. Diagnostic procedures based on analysis of the this gene or its expression are already in use for the analysis of benign and malignant alterations of the thyroid. Experimental protocols aiming at the functional expression of NIS in thyroid tumors or their metastases which lost capability for iodide uptake are currently developed. Furthermore, techniques are under investigation to express functional NIS by gene transfer in those benign or malignant tissues, tumors, metastases, which normally do not accumulate iodide. This would allow application of radioiodide therapy, a save and established technique to non-thyroid-related fatal diseases.