One Japanese study looked at the frequency of iodine-induced reversiblehypothyroidism. This type of hypothyroidism is not rare, and particularly in Japan, where iodine-rich seaweed is freqeuently eaten. In looking at 33 different people with hypothyroidism (25 women, 8 men) ranging in age from 21 to 77, stopped taking any iodine-containing drugs and foods
(i.e., seaweed products) for a total of up to 2 months. Their median TSH level, initially 21.9 was reduced
to a median of 5.3 mU/L after restricting iodine. 21of the patients had a reduction in TSH of more than 50%, 11 became euthyroid, with TSH levels within the normal range of 0.3-3.9 mU/L.
In the case of these patients more than half of the patients recovered from primary hypothyroidism after restricting iodine intake.
In Japan, the intake of iodine can range from a low of 0.1 mg/day to levels as high as 20 mg/day. (By way of comparison, a typical multivitamin in the U.S. may have from 75 mcg [0.000075 grams]. Most table salt in the U.S., however, is iodized, meaning that it has iodine added.)
The younger generation in Japan typically eats low-iodine westernized food, while the middle-aged and older generation frequently eat iodine-rich seaweed.
Should you restrict iodine? Should you supplement iodine? Iodine continues to be a controversial topic for thyroid patients. Read more about iodine now.
Source: Kasagi, Kanji, et. al., " Effect of Iodine Restriction on Thyroid Function in Patients With Primary Hypothyroidism," Thyroid, 09/04/2003