Study Title:

Optimal iodine supplementation during anti-thyroid drug therapy for Graves' disease is associated with lower recurrence rates than iodine restriction.

Study Abstract

OBJECTIVE:
A relationship between iodine intake and the effectiveness of anti-thyroid drug (ATD) therapy for Graves' disease (GD) has been suggested and strict restriction of iodine intake has been tried in the treatment of GD in some studies. However, it is unclear whether dietary iodine supplementation improves the prognosis of ATD therapy for GD. This study aimed to clarify whether optimal iodine supplementation during anti-thyroid drug therapy for GD is associated with lower recurrence rates than iodine restriction.

METHODS:
This was a prospective randomised trial of newly diagnosed patients with GD. Patients with newly diagnosed GD were recruited. After ATD therapy and strict dietary iodine restriction for one month, patients (n=459) were randomly assigned to iodine supplemented and iodine restricted groups. After exclusion, 405 patients finally completed the study. The iodine supplemented group included 203 patients (61 males and 142 females) with an average age of 32.2±10.5 years (17-65 years), and the iodine restricted group included 202 patients (61 males and 141 females) with an average age of 31.9±11.8 years (16-64 years). Patients in the iodine supplemented group were given about 10 grams of iodized salt every day, while the iodine restricted group received non-iodized salt with low-iodine or non-iodine diet. The dietary iodine intervention lasted for 24 months. Urinary iodine concentration (UIC), thyrotropin receptor antibody (TRAb), free T3 (FT3), free T4 (FT4) and thyrotropin (TSH) of two groups were measured every three months. The recurrence rates within 12 months after withdrawal of ATD was evaluated.

RESULTS:
UIC in the iodine supplemented group was within the recommended range for optimal iodine intake (135-162ug/L) and was significantly higher than that in iodine restricted group (30-58μg/L). Within 12 months of withdrawal of ATD, the total recurrence rate in the iodine supplemented group was 35.5%, significantly lower than in the iodine restricted group, which was 45.5%.

CONCLUSION:
Optimal dietary iodine supplementation during anti-thyroid drug therapy for GD is associated with lower recurrence rates than iodine restriction, and therefore diet control with strict iodine restriction might be an adverse factor in the management of GD. This article is protected by copyright. All rights reserved.

This article is protected by copyright. All rights reserved.

KEYWORDS:
Graves’ disease; Iodine; Iodine restricted; Iodine supplemented; recurrence rate

Study Information

Clin Endocrinol (Oxf). 2017 Dec 29. doi: 10.1111/cen.13543. [Epub ahead of print]

Full Study

https://www.ncbi.nlm.nih.gov/pubmed/29288501