Abstract: ObjectiveTo investigate the correlation between sodium/iodide symporter and thyroid stimulating hormone receptor expression in human thyroid cancer . Methods mRNA levels, quantified by real-time PCR, and protein evaluated by immunohistochemistry, were examined in surgical specimens of 18 normal thyroid tissues and 23 thyroid carcinoma tissues. ResultsThe NIS and TSHR mRNA levels of thyroid carcinoma were significantly lower than those of normal thyroid tissue and nodular goiter（P<0.005). In addition, there was a significant positive correlation between NIS and TSHR in normal thyroid samples (r=0.667, P=0.000）, but no such correlation in thyroid carcinomas（r=0.222，P=0.376）. The immunohistochemistry results showed that the NIS protein mainly located in cytoplasm, and TSHR protein mainly located in cytoplasm and cytomembrane .In thyroid carcinomas, the positive rates of NIS and TSHR protein were markedly higher than those in normal thyroid tissues（P<0.05). Through combined analysis of NIS mRNA concentrations and immunostaining scores, in the thyroid carcinomas, reduction of NIS mRNA expression with increment of intracellular protein was found in 74% (17/23) of the samples compared with normal tissues. ConclusionIn thyroid carcinomas, there were expressed contradiction and non-correlation between NIS and TSHR expression. NIS was not able to play the role of protein transporting and absorbing iodine as mainly located in cytoplasm, which was regarded as an important reason of radioiodine therapy failure for thyroid carcinoma.