Lack of Association between Urinary Iodine Excretion
and Successful Thyroid Ablation in Thyroid Cancer
Hernan P. Tala Jury,* Maria Grazia Castagna,* Carla Fioravanti, Claudia Cipri,
Ernesto Brianzoni, and Furio Pacini
Unit of Nuclear Medicine (E.B.), Macerata Hospital, 62100 Macerata, Italy; and Section of Endocrinology
and Metabolism, Department of Internal Medicine, Endocrinology, and Metabolism and Biochemistry
(H.P.T.J., M.G.C., C.F., C.C., F.P.), University of Siena, 53100 Siena, Italy
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, n125) or recombinant human TSH (rhTSH group, n76). 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 the time of
ablation was 132160g/liter, not significantly different between patients of theTHWand rhTSH
groups. There was no significant difference in UIE between ablated or nonablated patients both
in the whole group and the rhTSH or THW groups. According to the criterion of no visible uptake
plus undetectable stimulated serum Tg (in anti-Tg negative patients) at control WBS 8–12 months
after ablation, UIE was not significantly different in ablated and nonablated patients.
Conclusions: Our study indicates that the body iodine content is not an important determinant of
thyroid ablation, when preparing the patients with either THW or rhTSH. (J Clin Endocrinol Metab
95: 230–237, 2010)