Are there any known risk factors for the development of autoimmune (Hashimoto) thyroiditis?
Leonard Wartofsky, MD: The greatest risk factor for development of autoimmune Hashimoto thyroiditis is a family history. If one has not chosen their parents very well and instead has a parent and family history of autoimmune thyroid disease, they are at great risk of Hashimoto thyroiditis. There are animal studies, particularly in beagle dogs, that show that feeding an iodine-rich diet will produce a thyroiditis that histologically looks like Hashimoto thyroiditis. The dogs will have positive antibodies.
It is curious that Hashimoto thyroiditis does have a much higher prevalence and incidence in the United States, which has a higher iodine intake than in most countries in Europe, some of which may still be iodine deficient. So we see much more Hashimoto thyroiditis and there is higher iodine intake. If we extrapolate this population finding with the experimental data in dogs, the answer would indicate that iodine excess somehow can trigger either Hashimoto thyroiditis or something that looks and behaves like it.