I just started reading this book ...

The Thyroid Sourcebook, 5th Edition
M. Sara Rosenthal, Ph.D. 2009

I now regret starting to read it because some of what she says doesn't sound right, so now I can't take any of it seriously. It's difficult to figure out what to believe these days.

I'm glad I didn't pay for the book!

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We know that a lack of Iodine can cause the thyroid gland to enlarge. However, too much Iodine is believed to be responsible for triggering goiters and thyroid disorders as well. That’s one reason why taking kelp (seaweed) is not recommended. If you live in North America, you’re probably getting enough Iodine in your diet from your food thanks to iodized salt. Taking kelp with the belief that it will prevent a thyroid problem is a bad idea. It may trigger a thyroid problem instead of preventing one. In North America, except for advising you against taking kelp, physicians do not generally issue warnings to people at risk for a thyroid disorder about avoiding food containing iodine. That’s because iodine is found in a host of different foods that offer important nutrients. Since iodine is present in so many foods, it’s unlikely that someone will suffer from iodine deficiency in North America.

The Problem with Excess Iodine
In countries where iodine has been made plentiful in the food supply, such as in the United States, hypothyroidism from iodine deficiency has disappeared. However, hypothyroidism from autoimmune disease has skyrocketed.
It seems that excess iodine in the diet stimulates the immune system to create antibodies that attack the thyroid gland and cause it to stop making normal amounts of thyroid hormone, a condition called Hashimoto’s thyroiditis (see Chapter 2). Also, among people who get thyroid cancer, iodine supplementation has changed the types of thyroid cancer, decreasing the proportion of follicular thyroid cancers and increasing the number of papillary thyroid cancers. The reasons why iodine supplementation does these things are unknown. In healthy people who take very high doses of iodine once in a while, such as using iodine-containing water-purifi cation tablets on a camping
trip, excess iodine temporarily shuts off the thyroid gland and reduces its production of thyroid hormone. However, healthy thyroids will usually regain the ability to make thyroid hormone despite continued exposure to high iodine levels.