Randomised controlled trial of one week strict low-iodine diet versus one week non-specified low iodine diet in differentiated thyroid carcinoma

Introduction: A low iodine diet (LID) is recommended prior to the Radioactive Iodine-131 (RAI) treatment or scanning in differentiated thyroid carcinoma (DTC) post total thyroidectomy. However, recommended strictness of LID is varying among major guidelines. This study was aim to investigate the patient’s compliance to LID by measuring the urinary iodine level post LID. Methods: A total of one hundred and four patients of DTC post total thyroidectomy patients that were planned for treatment or scanning were enrolled into the study. 55 patients are subjected to 1-week strict LID while the other 49 patients are subjected to 1-week non-specified LID before RAI administration. Baseline urinary iodine level were obtained prior to the LID and second urinary iodine level were measured at day-8 or prior to RAI administration. Results:The compliance rate of patients that achieved urinary iodine level less than 100ug/L following 1-week strict LID was 89.1% as for the 1-weeks non-specified LID was 91.8% which did not show any significant difference between the two LID group (p=0.746). After 7 days institution of non-specified LID, the mean urinary iodine level was significantly reduced about 40.8% compared to strict LID (36.3%). Conclusion: The 1 week of non-specified LID is effective enough to decrease the urinary iodine level in low iodine intake area and the longer duration of LID is more hindrance for the patient to comply.