Few of us give much thought to the thyroid gland. This butterfly-shaped organ at the base of the neck keeps us feeling energetic and keeps our metabolism humming smoothly. The thyroid also guides the growth and development of the brain, starting on the day of conception. Yet it is vulnerable to toxins in our environment. Several studies have linked thyroid disorders to industrial chemicals, pesticides, herbicides and even the antibacterial compounds now found in soaps and toothpastes.

This exquisite gland is perfectly designed to keep thyroid hormones at just the right level to control the amount of energy we have. When levels dip, we become fatigued, sluggish and foggy in the brain. If levels are too high, our minds race, our hearts speed up, and we feel irritable.

What's a Thyroid?
The thyroid gland controls energy level, body temperature, metabolism, development and growth. It excretes hormones that can travel to every part of the body, including the brain, where they can affect mood.

Problems with the thyroid usually result in too little or too much hormone being produced. An overactive thyroid (hyperthyroidism) can cause nervousness, weight loss, a racing heart and a feeling of being too warm. Too little activity (hypothyroidism) causes tiredness, weight gain, memory loss, depression and reduced fertility. Since thyroid hormones regulate the development of the brain in utero, low thyroid levels during pregnancy can have lasting effects on a child's IQ and behavior.

Keeping the thyroid on an even keel is important for everyone, but it is perhaps most important for women of childbearing age. Women are twice as likely as men to suffer from thyroid problems. This is especially true after giving birth, when about 5 percent of women make either too much or too little of the hormones. About one-third of those women will never return to normal levels and require lifelong thyroid hormone treatment.

In the months following the birth of a child, thyroid problems can be mistaken for postpartum depression. Keeping thyroid hormones at the right levels after birth is important for making sure that new moms have the energy they need to take care of their babies.

Not only do thyroid hormones help new moms cope with childcare, but they are crucial for ensuring that pregnant women give birth to healthy babies. Women with low thyroid hormone levels are at risk of giving birth to children who have developmental delays and lower scores on intelligence quotient (IQ) tests. Studies have shown that children born to mothers with low levels scored, on average, 7 points lower on IQ tests than children whose mothers had normal thyroid levels.

For the first 10 weeks after conception, the fetus is completely dependent on the mother to supply thyroid hormones. These first 10 weeks are a critical time in brain development. That is why it is so important that mom make enough to share with baby.

Several factors have long been known to influence thyroid function. Thyroid disorders tend to run in families. Low iodine intake can depress thyroid activity, and exposure to radioactivity can damage the gland. In addition to these factors, newer research suggests a harmful role for the following chemicals in our environment:

Exposure to polychlorinated biphenyls (PCBs) in the womb can lead to reductions in the level of infant thyroid hormone. Many researchers believe this disrupts brain development and leads to lower IQ and behavioral issues in children. Since the banning of PCBs in the 1970s, researchers are finding fewer cases of impaired brain development due to these chemicals, according to recent studies.

Triclosan, an antibacterial chemical added to soaps, toothpastes, bath towels and many other products, interferes with thyroid hormones in North American bullfrogs, leading to limb deformities, according to a study published in the December 2006 issue of Aquatic Toxicology. When it comes to the thyroid system, the similarities between humans and amphibians are enough to give scientists cause for concern.

Plastic-softening phthalates have been found to reduce thyroid hormone levels in men. These chemicals are commonly found not only in plastics but also in consumer products (whose labels may list them as "fragrance"). Because they are so broadly used, phthalates may affect a large number of people.

Perfluorooctanoic acid (PFOA) is an industrial chemical used to make nonstick cookware, microwave popcorn bags, stain-resistant clothing, and many other products. PFOA does not readily break down and is now found in the bodies of many Americans. Research has linked PFOA to low thyroid activity, and some animal studies have found an association between PFOA exposure and thyroid tumors in rodents and monkeys.

Flame-retardant polybrominated diphenyl ethers (PBDEs) have been found in several studies to disturb thyroid function. They are also widely detected in house dust and in the bodies of most people in this country and are linked to behavioral and developmental problems.
Perchlorate is a thyroid toxin used to make fireworks and rocket fuel. Several pockets of groundwater contaminated with perchlorate exist around the nation. The chemical has been found in milk and lettuce produced in the United States and is also found in human breast milk. Pregnant women who ingest perchlorate and develop low thyroid levels are at risk of giving birth to infants with developmental difficulties.

Found in plastics and the liners of food cans, including baby formula, bisphenol A (BPA) can alter the function of thyroid hormone in the brain, potentially leading to the development of attention deficit hyperactivity disorder.

What you can do
If you are pregnant, be screened for thyroid disorders as soon as possible.
Tell your obstetrician if there is a family history of thyroid disorders or autoimmune disorders such as juvenile (type 1) diabetes, rheumatoid arthritis, pernicious anemia due to a lack of vitamin B12, or colitis.
Check your neck: watch for any swelling or painfulness in the thyroid area.
Most Americans consume enough iodine in their diet, but if you don't use iodized salt or eat fish, you may not be getting enough. Talk to your doctor about your iodine intake.
Have your water tested if you suspect contamination from perchlorate, pesticides or herbicides. This is especially important if you drink well water.


Photo credit: http://www.flickr.com/photos/trekkyandy/ / CC BY-SA 2.0


Although it hasn't been part of any official evaluation of perchlorate toxicity, it has been known since 1968 that the autoimmune effects of medicinal doses of perchlorate are a form of drug-induced lupus. See Beickert and Heinicke 1968 pubmed id 4181403. In nursing infants the corresponding sign of perchlorate toxicity would be the rash known as Sweet's syndrome.

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