Objective: To observe the influence of different doses of iodine intake on the expressions of thyroid-stimulating hormone receptor (TSHR) mRNA and sodium/iodide symporter (NIS) protein in thyroid tissue of rats. Methods: Thirty-six SD rats were equally randomized into low iodine group, normal iodine group and high iodine group. Half of the number of rats of each group were sacrificed at the end of 4 and 8 weeks, respectively. The expressions of TSHR mRNA and NIS protein in the rats’ thyroid tissues were determined by real-time PCR and immunohistochemical staining, respectively. Results: Compared with the normal iodine group at the end of 4 weeks of the experiment, the TSHR mRNA expression level in low iodine group significantly increased (P<0.05), and slightly decreased in high iodine group but the difference had no statistical significance (P>0.05); the NIS protein expression in low iodine group increased to some extend and somewhat decreased in high iodine group, but both differences reached no statistical significance (both P>0.05). Compared with the normal iodine group at the end of 8 weeks, the expressions of TSHR mRNA and NIS protein in both the low iodine and high iodine group were significantly reduced (both P<0.05), in which the NIS expression levels dropped to 44.03% and 56.12% of what they had reached at the end of 4 weeks, respectively (both P<0.05). Conclusion: In either iodine-excessive or iodine-deficient conditions, the long-term iodine disorder can decrease NIS expression, which is possibly mediated by the alterations of the TSH-TSHR signaling activity.