Utility of a low-iodide diet in (131)I whole body scanning of patients with differentiated thyroid cancer.

Introduction: (131)I whole body scanning (WBS) is useful in the follow-up of patients with differentiated thyroid carcinoma (DTC). The need to follow a low-iodide diet (LID) to optimize WBS is widely recognized but there are few reports that justify this practice. The aim of this study was to assess levels of urinary iodide in patients who underwent WBS in our service and the possible impact of some changes to the diet on these levels.

Patients And Method: Between January 2004 and December 2005, we measured iodide levels in 12-h urine samples by paired-ion-reversed-phase HPLC with electrochemical detection (sensitivity, 0.1 μg/dl) in 371 patients with DTC referred to our service for ablation or follow-up. The patients were divided into 2 groups: patients on hormone withdrawal and strict LID (group A) and those on hormone withdrawal and generic LID (group B). Urinary iodide excretion below 10 μg/dl was considered low. Data were analyzed by ANOVA and χ(2) tests.

Results: The mean±standard deviation urinary iodide excretion was 4.3±3 μg/dl in group A and 5.8±3.2 μg/dl in group B. The mean urinary iodide excretion in A group was significantly lower than that in group B (p<0.05).

Conclusions: Following a strict LID significantly decreased urinary iodide excretion in patients undergoing WBS.