These phenomena have also been found in the study by Xing et al,33 indicating that other factors may be involved in the regulation of the expression of Tg and Tpo. 34 Moreover, TPO was not obviously elevated in our study, which may compromise the final lethal effect of radioiodine on tumour cells, due to that iodide anion not organized by TPO undergoes rapidly efflux from cells, and a balance between NIS‐mediated iodide uptake and TPO‐mediated efflux determines the intracellular concentration and radiation dose of radioiodine.35 This evidence concerns the gene SLC5A5 and neoplasm.