Last night, I heard Dr. Joseph Pizzorno speak. He's written many books on health and was founded and president of Bastyr U, the naturopathic school.
He spoke about toxicity and correlation with health problems, diabetes, cancers, and yes, thyroid. He's very analytical and discussed how anywhere in the world, people are toxic, though the specific toxic load varies, depending on where you are.
Just thought I'd throw it out there that a good proportion of our thyroid problems are likely linked to toxins.
What can you do?
Eat organic. Filter your water. Eat a lot of vegetables to provide fiber. Sweat.
There are tests for heavy metals and other pollutants. For metals, a provoked urine test is best.
He suggested taking 250mg of DMSA every third day, 5g of extra fiber and 1g of N-acetyl-cysteine daily to slowly get rid of toxins.