This study aimed to correlate I-131 uptake in the remnant thyroid gland with TSH-stimulated Tg levels (off-Tg) and evaluate available clinical and pathologic findings that may influence RAI ablation success in a fully functional thyroid gland in real-world clinical setting, which may be helpful in determining repeat I-131 treatment in thyroid cancer RAI ablation or metastasis. The gene discussed is TG; the disease is thyroid cancer.