三种脱碘酶硒酶是细胞内甲状腺激素（TH）水平的重要调节因子。两种甲状腺激活脱碘酶（D1和D2）通常表达于滤泡甲状腺细胞中，并有助于总体TH的产生。在甲状腺肿瘤发生过程中，脱碘酶表达谱发生变化，以满足癌细胞不同的TH水平需求。分化型甲状腺癌会过度表达TH失活的D3，以减少肿瘤内的TH信号。惊人的是，最近的证据表明，在甲状腺肿瘤发展的晚期，D2表达升高，而D3表达水平降低，这会增加非分化型甲状腺癌细胞的TH细胞内信号。这些发现对甲状腺癌不同阶段TH的功能提出了质疑。

The three deiodinase selenoenzymes are key regulators of intracellular thyroid hormone (TH) levels. The two TH-activating deiodinases (D1 and D2) are normally expressed in follicular thyroid cells and contribute to the overall TH production. During thyroid tumorigenesis, the deiodinase expression profile changes to customize intracellular TH levels to different requirements of cancer cells. Differentiated thyroid cancers overexpress the TH-inactivating D3, likely to reduce the TH signaling within the tumor. Strikingly, recent evidences suggest that during the late-stage of thyroid tumorigenesis D2 expression raises and this, together with a reduction in D3 expression levels, increases TH intracellular signaling in dedifferentiated thyroid cancers. These findings call into question the different function of TH on the various stages of thyroid cancers.