Many environmental toxins are endocrine disrupting chemicals. Some interfere with thyroid function by reducing thyroid stimulating hormone (TSH) and thyroxine. Examples include polychlorinated biphenyls, dioxins, phthalates, polybrominated diphenyl ethers and other halogenated organochlorines. High levels of hypothyroidism are seen with PCB and heavy metal exposure.

The incidence of thyroid disease, especially cancer and autoimmune disease, is increasing, rapidly. Clinically significant hypothyroidism can be defined when the TSH is over 4.5 mU/L? and the thyroxine (T4) is less than 4.5 mcg/dL. About 7% of the population had hypothyroidism in the U.S. in 1994. Subclinical hypothyroidism is diagnosed when the TSH is over 4.5 and the T4 is over 4.5. Hyperthyroidism is diagnosed when the TSH is less than 0.1 the T4 is over 13.2. TSH increases with aging, normally.

Thyroid autoimmune disease (TAD) is seen in 24 million people, currently. This includes Hashimoto’s thyroiditis, idiopathic myxedema, asymptomatic thyroiditis, endocrine exophthalmos and Graves’ disease. TAD is often diagnosed in conjunction with other autoimmune diseases. This may be due to environmental disruptors.

Thyroid disruptors can cause fetal neurodevelopmental damage. Thyroid hormone is necessary for the development of the central nervous system, pulmonary system, cardiovascular system and other organs. The first trimester of pregnancy is important for neurodevelopment. Hypothyroidism in pregnant mothers can result in abnormal intellectual development in the baby.

Hypothyroidism increases the risk of heart disease in the elderly. Total cholesterol, low-density lipoproteins (LDL) and total triglycerides increase while the high-density lipoproteins (HDL) decrease in hypothyroidism.

Thyroid disruptors are environmental chemicals which alter thyroid function. The main dysruptors are PCBs, bisphenol A, perchlorate, dioxins (TCDD and PCDF,) pentachlorophenol, phthalates, etc. There is increasing evidence that parabens (of cosmetics) and pesticides (DDT, chlordane, etc.) are thyroid disruptors.

Total T4 is the best indicator of thyroid disruption. Perchlorate has been widely studied and is found in soils, water in Chile, mother’s milk, grains, vegetables, supplements and food crops for livestock. The groundwater of the western U.S. contains perchlorate from industrial and waste storage sites. Perchlorate suppresses T3 and T4.

Polychlorinated biphenyls (PCBs) are thyroid disruptors and are carcinogenic. Their use has been restricted since 1977, but, they remain in the environment for a long time. Higher concentrations occur in animals higher in the food chain, at a level up to 1 million times that found in a contaminated drop of water.

PCBs damage the body in many ways. They are associated with thyroid damage, thyroid cancer and lower blood levels of thyroid hormones. Fish contain PCBs, including the salmon from Alaska. Prenatal exposure to PCBs impairs cognitive function in infancy and in childhood. The body burden of PCB can be reduced by 16-20 g of olestra daily for a “prolonged” time.

CONCLUSION: Thyroid disease, autoimmune thyroid disease and thyroid cancer are significant problems at this time. Much of the current thyroid disease comes from thyroid disruption resulting from a wide range of environmental contaminants.

NOTE: Perchlorate is from jet fuel which contaminates our city water supplies. Perchlorate is a serious problem in the Little Colorado River of northern Arizona.

Read about the effect of thyroid disruption on the blood lipid profile of patients.

To read the author’s abstract of the article click on the link to the author’s title of the article above.

PMID: 20030460.

Summary #375.