Lack of Association between Urinary Iodine Excretion and Successful Thyroid Ablation in Thyroid Cancer Patients

Background: Low-iodine diet is prescribed before 131I administration in patients with differentiated thyroid cancer, although no study has properly quantified its clinical benefit. Objective: Our study aimed to evaluate the association between urinary iodine excretion (UIE) and 131I ablation by correlating UIE with the rate of successful ablation. Patients: We retrospectively studied 201 differentiated thyroid cancer patients who had received 131I therapy and posttherapy whole-body scan (WBS) for remnant ablation after either thyroid hormone withdrawal (THW group, n = 125) or recombinant human TSH (rhTSH group, n = 76). The outcome of thyroid ablation was assessed using two different criteria: no visible uptake at control WBS 8–12 months after ablation or no visible uptake plus undetectable stimulated serum thyroglobulin (Tg). Results: According to the criterion of no visible uptake, 84.6% of the patients were successfully ablated, with no significant difference between THW and rhTSH groups. Mean UIE at t...