While generally well-tolerated, its efficacy is limited, as nearly 50% of persistent, recurrent, or metastatic lesions lose iodine avidity through de-differentiation and downregulation of sodium iodide symporter (NIS) or thyroid peroxidase expression, leading to RR-PTC (radioiodine-refractory papillary thyroid cancer) [17,18]. The gene discussed is SLC5A5; the disease is thyroid gland papillary carcinoma.