Thyroid gland and the environment

Townsend Letter for Doctors and Patients,  Dec, 2004  by Rose Marie Williams

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Well-recognized thyroid expert, Broda Barnes, MD, estimated approximately 40% of the American adult population suffers from undiagnosed hypothyroidism. Subnormal thyroid function appears to be a risk factor for cancer. Iodine is a major component of the thyroid gland. Improper thyroid function, be it hypothyroid, or hyperthyroid, appears to be a risk factor for cancer among the general population. (1)

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Iodine deficiency has been associated with breast cancer risk. Iodine deficiency can be a matter of geography, or induced by any number of environmental stressors. Dr. Bernard Eskin, Director of Endocrinology in the Department of Obstetrics and Gynecology at the Medical College of Philadelphia found an association between iodine deficiency and breast cancer. Dr. Eskin's research uncovered a high incidence of breast cancer in iodine poor areas of the United States, Poland, Switzerland, and Austria, where goiter is also predominant. Japan and Iceland have the world's lowest rates of goiter and breast cancer deaths. Iodine rich sea vegetables are important staples of Japanese cuisine, and iodine rich seafood makes up a large part of the Icelandic diet. (1)

In addition to dietary deficiencies, thyroid function can be adversely affected by drugs, chemical pollutants, and radiation exposure. (1)

Drugs and Chemicals

Manmade compounds also assault the thyroid gland. Thyroid function can be suppressed by certain drugs and chemicals--antidiabetic and sulfa drugs; barbiturates that contain cyanide; prednisone; estrogen (birth control pills and hormone replacement therapy); some cough medicines; the antidepressant lithium; aspirin and other salicylate painkillers; and thousands of chemical food additives in processed food. (1,2)

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Perchlorate is a potent environmental toxin that inhibits iodine uptake by the thyroid gland. Perchlorate is a by-product of synthetic fertilizers and solid propellants for rockets, missiles, and fireworks. Perchlorate salts are a component of airbag inflators. It has been leached into surface and underground water supplies. (1)

Pesticides used on domestic and international air flights pose an additional risk to thyroid suppression. Tralomethrin, a commonly used airline pesticide spray, contains bromide, which caused thyroid disease in animal studies. (1)

Fluoride

"Statistics show that populations drinking fluoridated water have universally lower thyroid levels," states Jerry Mittelman, DDS, editor of The Holistic Dental Digest PLUS. Fluoride is an intensely controversial subject, praised by some for protecting against tooth decay, and condemned by others as a major risk factor for cancer, arthritis, osteoporosis, and hypothyroidism. (3,4)

It is almost impossible to avoid fluoride in our culture. Fluoride is added to more than half the municipal water supplies in the US. Bottled juices, soft drinks, iced teas, wine coolers, jellies, and other processed foods are often made with fluoridated water. If consumers wish to know if their favorite brand of bottled or canned beverage is made with fluoridated water, they must call the company and ask.

Nearly all supermarket brands of toothpastes, and many brands sold in health food stores contain fluoride. However, it is possible to find some brands of toothpaste in health food stores that do not contain fluoride.

Our exposure to fluoride can start during infancy, and in some cases in utero. Some brands of baby foods contain high levels of fluoride. Children may be given fluoride tablets or rinses at school, or by their dentist. (5)

Studies done with Danish female cryolite workers showed fluorosis in the teeth of offspring that had been nursed, raising the possibility that fluoride can even be passed through breast milk. Cryolite is a compound of aluminum, sodium and fluorine. There are animal studies that show fluoride's effect on fertility and that it easily crosses the placenta. Richard Foulkes, MD, indicates that, "after 46 years of fluoridating drinking water, no study had taken place on the effect of fluoride on the developing fetus!" (6) How long-term exposure to fluoride may affect the thyroid glands of Americans is not known, nor does there seem to be much interest in finding out.

Tobacco and Alcohol

One of the nasty ingredients in cigarette smoke is thyocyanide, a strong thyroid inhibitor that further compounds the many health risks of heavy smokers and those around them. Smoking harms the thyroid gland by decreasing the thyroid's ability to secrete hormones, and by limiting the hormones' action. Smokers are more prone to have enlarged thyroid glands indicating subclinical hypothyroidism. (1)

Alcohol is a highly refined carbohydrate, and requires the whole complement of B vitamins for proper metabolism. A deficiency of B-6 reduces the thyroid's ability to convent iodine into thyroid hormone. (1)

Soy and Other Foods

Some foods including soy, walnuts, cabbage, cauliflower, and kale can contribute to low thyroid function if eaten frequently, and in large amounts. Hypothyroid individuals are advised to consume these items cautiously until their condition is corrected with supplemental thyroid medication. (1)