Low iodine diet does not improve the efficacy of radioiodine for the treatment of Graves’ disease

Abstract

Objective: Consuming a low-iodine diet (LID) is a widely accepted practice before administering radioiodine ( 131 I) to evaluate and to treat thyroid disease. Although this procedure is well established for the management of patients with differentiated thyroid cancer, its use in patients with benign disease is unclear. So, we aimed to evaluate the influence of a LID on the outcome in patients with Graves' disease (GD) treated with 131 I. Subjects and methods: We evaluated 67 patients with GD who were divided into 2 groups: one group (n = 31) consumed a LID for 1-2 weeks, and the second group (n = 36) was instructed to maintain a regular diet (RD). Results: The LID group experienced a 23% decrease in urinary iodine after 1 week on the diet and a significant 42% decrease after 2 weeks on the diet. The majority (53%) of the patients in the LID group had urinary iodine levels that were consistent with deficient iodine intake. However, there was no difference in the rate of hyperthyroidism's cure between the LID and the RD groups 6 months after 131 I therapy. Furthermore, the therapeutic efficacy did not differ in patients with varying degrees of sufficient iodine intake (corresponding urinary iodine levels: < 10 μg/dL is deficient; 10-29.9 μg/dL is sufficient; and > 30 μg/dL is excessive). Conclusion:In the present study, we demonstrated that although a LID decreased urinary iodine levels, those levels corresponding with sufficient or a mild excess in iodine intake did not compromise the therapeutic efficacy of 131 I for the treatment of GD. Arch Endocrinol Metab. 2015;59(6):501-6

Influence of Short-Term Dietary and Therapeutic Iodine Restriction on the Therapeutic Effects of Radioactive Iodine Therapy in Patients with Graves' Disease

“…The remission rate observed in this study was similar to rates in previous studies (57.8% (10) and 50.0% (11)) in Japanese patients with Graves' disease (Supplementary Table S3). On the other hand, previous reports from western countries (1)(2)(3)12,13) showed a higher remission rate for RAIT. In particular, Isgoren et al ( 12) reported a higher remission rate for Graves' disease treated with RAIT than the present study, although the duration of ATD discontinuation before RAIT was shorter and the therapeutic dose of radioactive iodine used was smaller.…”

“…In the other group, the patients were not instructed to restrict dietary iodine intake. When they compared therapeutic effects after 6 months between the iodine intake restricted and non-restricted groups, they found that dietary iodine was not associated with the therapeutic effects (13). Accordingly, their study suggests that dietary iodine restriction may not be necessary.…”

High Thyroid Stimulating Receptor Antibody Titre and Large Goitre Size at First-Time Radioactive Iodine Treatment are Associated with Treatment Failure in Graves’ Disease

“…However, a recent study had demonstrated that the efficacy of RAI therapy in GD was not compromised by iodine nutritional status even when patients presented with urinary iodine excretion that is compatible with mildly excessive iodine ingestion. 21 Another limitation of our study is the lack of uniform strategies in the selection of RAI dosage to treat patients. Many institutions in Europe prefer the use of empirical over calculated RAI dosing strategies.…”

Success Rate of Radioactive Iodine Therapy in Graves’ Disease Using Dose Corrected for Thyroid Gland Size

“…21 However, the prospective study by Santarosa et al showed no difference in the rate of hypothyroidism 6 months after RAI therapy between patients with Graves' disease patients who consumed low-iodine diet and patients who took regular diet (86.7% vs 82.6%, p value = 0.74). 22 Lastly, since most of the patients had been referrals from other hospitals, some patients who had a higher chance to be cured with a single dose of I-131, such as patients with small gland size or mild hyperthyroidism, had been referred back to their primary hospitals for further follow-up. Thus, the assessment count of successful treatment numbers was difficult to achieve in our study results of this group of patients and this could lead to underestimation of treatment success.…”