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Effect of lifelong iodine supplementation on thyroid 131-I uptake: a decrease in uptake in euthyroid but not
M Milakovic1, G Berg, R Eggertsen
1Mölnlycke Primary Health Care and Research Centre, Department of Primary Health Care, Sahlgrenska Academy at Göteborg University, Sweden.
European Journal of Clinical Nutrition
|October 28, 2005
Summary
Iodine supplementation in Sweden has lowered the normal 24-hour radioiodine uptake in euthyroid individuals. This study found a reference interval of 14-30% for 24-hour iodine uptake in a supplemented population.
Area of Science:
- Endocrinology
- Nuclear Medicine
- Public Health Nutrition
Background:
- Sweden has implemented mandatory iodine fortification of table salt since 1936, increasing levels in 1966.
- This long-term iodine supplementation policy impacts thyroid function within the population.
Purpose of the Study:
- To assess 24-hour radioiodine uptake (24h IU) and thyroid nodularity in euthyroid individuals with lifelong iodine supplementation.
- To compare current 24h IU in euthyroid individuals with historical data and uptake in thyrotoxic patients.
Main Methods:
- Investigated a cohort of euthyroid individuals (n=44, aged 60-65) with lifelong iodine supplementation.
- Administered oral radioiodine (0.1 MBq 131-I) and performed thyroid scintigraphy using 99mTc-pertechnetate to measure 24h IU.
Main Results:
- The mean 24h IU in euthyroid individuals was 21% (reference interval 14-30%) in 1999-2000.
- Multinodular goitre was observed in three euthyroid individuals via scintigraphy.
- Graves' disease patients (n=53) showed a mean 24h IU of 61%, similar to historical hyperthyroid values.
Conclusions:
- The established reference interval for 24h IU in this iodine-supplemented population is 14-30%.
- This interval is lower than historical values from 1955, indicating an effect of long-term iodine supplementation.
- Radioiodine uptake in hyperthyroid patients appears unaffected by the population's iodine supplementation history.