Lee Swanson: Dr. Langer, why is there so much hidden hypothyroidism, under active thyroidism, in the American population? Dr. Stephen Langer: Well, you're asking me a tough question. Why? I think it's multifactorial and I don't think we know all the answers. One thing we do know is that toxins and pollutions in the environment can actually suppress thyroid function. Common chemicals, such as fluoride in the water, can affect thyroid; chlorine in drinking water can affect thyroid; heavy metals can affect thyroid and a lot of people are exposed to heavy metals. People who smoke cigarettes, cigarette smoke contains very low levels of cadmium which builds up over a lifetime can impact the thyroid, then there are genetic factors, there are probably nutritional factors, there are autoimmune factors. Now, by autoimmunity I mean your body's immune system is actually attacking the thyroid and can cause hypothyroid or low thyroid symptoms. Lee Swanson:Is that Hashimoto's disease? Dr. Stephen Langer: We were talking about Hashimoto's, but so in other words, we're talking about something that's fairly clinically complex, but bottom line is that Dr. Barnes who was my teacher this was back in the 40s when he published his first major clinical paper in The Journal of the American Medical Association; at that time felt that probably 40% of the American population had some form of subclinical hypothyroid symptoms and should probably if they were symptomatic clinically be put on a small dose of thyroid medication. I tend to agree. I don't know if it's 40%, but the numbers are astronomical.