One of the main roles of iodine is to help manufacture thyroid hormones. And once upon a time in America — especially in the Great Lakes region — there were many cases of goiter, an enlarged thyroid gland caused by iodine deficiency.
The iodine/goiter story had a happy ending, however, when manufacturers began adding iodine to salt ("iodized salt"). After that, goiters in the U.S. mostly disappeared.
But the iodine story turns out to have an epilogue. A new epidemic of iodine deficiency has occurred. And it's bringing a lot more than goiters with it.
Low iodine might also contribute to fatigue and chronic fatigue syndrome (CFS). A study showed that people with low body temperature and fatigue felt better and had more energy when they took a daily supplement of 1,500 micrograms (mcg) of iodine (the RDA is 150), though their temperature didn't rise.
It's reasonable for those with unexplained fatigue, CFS or fibromyalgia to add an iodine supplement (6-12 mg) daily for three months to see if it helps. You'll often see a marked increase in energy within the first month.
Low iodine has also been associated with weight gain.