Influence of the Ingestion of the Sea-weeds on the Thyroidal Uptake of I¹³¹

Abstract

In Japan sea-weeds are commonly taken as food. As they are relatively rich in iodine content, it is conceivable that the thyroidal uptake of radioactive iodine is inhibited by ingesting them. But there have been no precise reports concerning the effect of the ingestion of the sea-weeds on the thyroidal uptake of radioactive iodine.
In this report the effect of sea-weeds on the uptake of I¹³¹ by the thyroid gland was studied and the following results were obtained:
1. In ten normal persons tangle (Laminaria japonica), which is rich in iodine (0.31% of dry weight), was given between 7 to 16 gms. daily for one to fourteen days. In all cases remarkable inhibition of I¹³¹-uptake was observed. Uptake values returned to the previous level about two weeks after discontinuing the ingestion.
2. In seven persons laver (Enteromorpha compressa), which contains relatively small amount of iodine (less than 0.03% of dry weight), was given between 1.2 to 3.2 gms. daily for two to fourteen days, but in no cases the inhibition of I¹³¹-uptake was observed by these doses.
3. In four patients with Graves' disease 10 gms. of tangle was given for four to six days. In all cases I¹³¹-uptake was markedly inhibited, but the uptake values returned to the previous level about two weeks after cessation of the ingestion.
4. In five patients very low uptake values were observed due to the long term ingestion of tangle ranging from three months to ten years. About two weeks after discontinuing the ingestion the uptake values returned nearly to the previous level.
From these results it was stressed to pay special attention for the previous ingestion of sea-weeds in the I¹³¹-uptake study in Japan.