It has not been clearly investigated how iodine can be trapped from the extracellular space into thyroid follicular cells, the defective iodide-trapping mechanism appears to be an early and constant feature during oncogenic transformation of thyroid cells. In recent studies, NIS and pendrin are associated with the trapping process. Thus, in order to reveal this uncertain relationship, each of the quantitative expressions of NIS and pendrin in various thyroid tissues were evaluated by real time RT-PCR.

This study included 63 patients who had undergone thyroidectomy in Uijongbu St. Mary's hospital from Jan. 2000 to Jan. 2003. 13 cases of normal thyroid, 17 cases of hypofunctioning thyroid adenomas, and 33 cases of thyroid cancer were examined. The thyroid cancer group was further divided into high and low risk group according to the AMES score, and the NIS and pendrin levels were compared between the two groups. Real time RT-PCR was conducted with the extracted RNAs, using GAPDH as the control.

As for pendrin, its expression was decreased by 7% in the thyroid adenoma group compared with that of normal thyroid, while there was a 59% decrease in thyroid cancer cases. NIS expression was decreased by 20% in the thyroid adenoma group, and a 40% decrease was found in thyroid cancer group. Due to the impediment of pendrin in both high and low risk group of thyroid cancer, there was a 19% decrease in the high risk group compared with the low risk group. As for the impediment of NIS in the high risk group, an increase of 30% was found. However, no statistical significance was shown (P=0.344 vs P=0.688).

According to this study, it can be inferred that the decrease in the expressions of NIS and pendrin are related to tumorigenesis of thyroid cancer. Also, further research is needed to reveal the cause of genetic transformation, as well as the value of utilization of NIS and pendrin as tumor markers.