The factors regulating the function of NIS are of direct clinical importance due to its central role in radioiodide treatment; patients with radioiodide-refractory (RAIR) thyroid cancer, particularly those with metastatic disease, have a life expectancy of 3–5 years and represent a group for whom there remains a clear unmet medical need (1,2). The gene discussed is SLC5A5; the disease is thyroid cancer.