Ingesting iodine, much less deliberately fortifying salt for everyone to ingest, is the worst possible way to use it. Ingested iodine can lead to serious trouble, and does not produce the desired effect on the thyroid.
I ordered some potassium iodide from an organic supplement vendor. Indeed, the product directions said to take by mouth. I was directed in no uncertain terms to ignore that. I applied it transdermally.
Transdermal application has great advantage. You can't overdose. The skin will absorb a necessary amount, and no more. Wipe off the excess.
About 20 years ago, an inexperienced but eager PA started me on Levothyroxine for no good reason. It appears that no lasting damage was sustained by my thyroid.
Today, my TSH/T4/T3 levels are completely normal. I've been drug-free for over 12 months. Last week, my PCP agreed that there is no evidence of thyroid dysfunction.