Unlike other nutrients such as some vitamins, which can be megadosed without too many problems, the effect of iodine depends on the overall status of the organism. Cofactors are extremely important; if iodine was the problem, the Japanese wouldn't even exist anymore.
Too much iodine in the presence of other halogens in the tissues? You'll have a bad experience.
Too much iodine with a weak antioxidant system? You'll have a bad experience
Since iodothyronines can be used as antioxidants (sometimes even more potent than vitamin C and E), I believe that there is a possibility that a person will experience symptoms of hypothyroidism with high doses of iodine if too much of T3 and T4 are being “hijacked” to be used as antioxidants.
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