The growth inhibition effect of iodide on thyroid nodules depending on theexpression of the Na+/iodidesymporter

Background and Methods: We investigated 28 thyroid nodules (14 nodules with a decreased Tc-uptake and 14 nodules with increased Te accumulation). Also samples from para nodular surrounding tissue and from "normal" parenchyma were available as controls. The expression of the NTS gene was analysed wit h a (semi-)quantitative RT-PCR. Primary cell cultures from each tissue samp le were incubated for 24 and 72 hours with different concentrations of iodi de (10(-8), 10(-6), 10(-4) M) and the effect on cell growth was assessed. Results: Thyrocytes from "cold" nodules with a decreased NTS-expression sho wed an inhibition of growth of only 8+/-1.2%, whereas the growth inhibition effect of iodide on cell cultures derived from adenomas with augmented Tc- uptake and an increased NTS expression was 33.7 +/- 8.3%. In thyrocytes fro m tissues with normal NTS expression the cell growth could be reduced by 15 .6 +/- 2.6%. Conclusion: The results demonstrated that the growth inhibition effect of i odide on thyroid nodules depends on their expression of the NTS gene. This supports the role of iodide for prophylaxis of recurrent goiter after surge ry.