In thyroid cancer, chronic hypoxia within the tumor stimulates the production of hypoxia-inducing factors, thereby regulating key genes such as vascular endothelial growth factor, GLUT-1 (glucose transporter 1), P21, and carbonic anhydrase 9 to jointly promote tumor growth, invasion, and metastasis (57, 58). This evidence concerns the gene CA9 and thyroid gland carcinoma.