Effect of iodine restriction on short-term changes in thyroid function in patients with subclinical hypothyroidism
10.4163/jnh.2022.55.2.250
- Author:
Obin KWON
1
;
Dong Yeob SHIN
;
Eun Jig LEE
Author Information
1. Department of Biochemistry and Molecular Biology, Seoul National University College of Medicine, Seoul 03080, Korea
- Publication Type:Research Article
- From:Journal of Nutrition and Health
2022;55(2):250-262
- CountryRepublic of Korea
- Language:English
-
Abstract:
Purpose:Elevated iodine intake is related to a higher prevalence of subclinical hypothyroidism (SCH). We investigated the short-term effect of dietary iodine restriction on thyroid function in patients with SCH with high iodine intakes.
Methods:The iodine levels in 64 SCH patients with serum TSH levels from 4.0 to 10.0 mIU/L and normal serum fT4 levels (n = 64) were assessed using 24-hour urine iodine test results and iodine intake levels calculated using a semi-quantitative food frequency questionnaire.Dietary iodine restriction was not recommended for patients with an iodine intake in the normal range (group A, n = 13), but seaweed restriction was recommended for patients with high iodine intakes (group B, n = 33). Thyroid functions and iodine levels were rechecked after three months. Another eighteen patients were prescribed thyroid hormone replacement therapy according to clinical criteria.
Results:Median baseline iodine intake for the 64 patients was 290.61 μg/day, and median 24-hour urine iodine was 33.65 μmol/g of creatinine. The major source of dietary iodine was seaweed, which accounted for 72.2% of median baseline intake. Urine iodine and calculated iodine intake levels were positively correlated with serum TSH levels (p < 0.001 and p = 0.027, respectively), and calculated iodine intakes were significantly correlated with urine iodine levels (p = 0.001). In group B, iodine restriction significantly decreased urine iodine (p = 0.042) and TSH levels (p = 0.004), and conversion to euthyroid status was achieved in 16 of the 33 patients (48.5%).
Conclusion:Iodine intake and urine iodine levels are correlated with thyroid function in SCH patients, and dietary iodine restriction can aid functional thyroid recovery in patients with elevated iodine intakes.
