Re:

I don't know. Seems likely that its something in the diet that wasn't previously ubiquitous when goiter was more prevalent. Halogens have always been around.

Something is inhibiting the inflammatory response of the thyroid, that wasn't present previously in the masses' diets.

It might be bromide.

It could also be something as obscure as an artificial colorant, e.g., alizarin ("yellow #5") or some other artificial colorant / flavorant. The colorants are typically amino compounds which are psysiologically active, in ways having yet to be discovered, not to mention the trace amounts of impurities they contain.

Another possibility is large quantities of seed oils (esp. corn oil, but maybe soybean, etc.) Corn oil came in after WWII in "margarines".

Then again, the above all could be wrong, and it might be the tiny amounts of Iodide in iodized salt are just barely sufficient to keep goiter from showing up. Lots of folk take "vitamin pills" and those usually contain some tiny amount of iodide.

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