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Thyroid Disease
Endocrine Resource Center

Adapted by Mary Shomon


More than 10 million Americans have been diagnosed with thyroid disease, and another 13 million people are estimated to have undiagnosed thyroid problems in the U.S. alone. Frequently misunderstood, and far too often overlooked and misdiagnosed, thyroid disease can affect almost every aspect of health, so understanding more about the thyroid, and the symptoms that occur when something goes wrong with this small gland, can help you protect or regain good health health.

A February, 2000
research study found that the estimated number of people with undiagnosed thyroid disease may be 10 percent -- a level that is double what was previously thought. This may mean as many as 13 million Americans are currently undiagnosed. For women, the risk is even higher. A woman faces as high as a one in five chance of developing thyroid problems during her lifetime. That risk increases with age and for those with a family history of thyroid problems.

What is the Thyroid?

Your thyroid is a small bowtie or butterfly-shaped gland, located in your neck, wrapped around the windpipe, and is located below the Adam's Apple area. The thyroid produces several hormones, of which two are key: triiodothyronine (T3) and thyroxine (T4).

The thyroid has cells that are the only cells in the body's capable of absorbing iodine. The thyroid takes in the iodine, obtained through food, iodized salt, or supplements, and combines that iodine with the amino acid tyrosine. The thyroid then converts the iodine/tyrosine combination into the hormones T3 and T4. The "3" and the "4" refer to the number of iodine molecules in each thyroid hormone molecule.

When it's in good condition, of all the hormone produced by your thyroid, 80% will be T4 and 20% T3. T3 is considered the biologically more active hormone -- the one that actually functions at the cellular level -- and is also considered several times stronger than T4.

Once released by the thyroid, the T3 and T4 travel through the bloodstream. The purpose is to help cells convert oxygen and calories into energy.

As mentioned, the thyroid produces some T3. But the rest of the T3 needed by the body is actually formed from the mostly inactive T4 by a process sometimes referred to as "T4 to T3 conversion." This conversion of T4 to T3 can take place in some organs other than the thyroid, including the hypothalamus, a part of your brain.

The thyroid is part of a huge feedback process. The hypothalamus in the brain releases something called Thyrotropin-releasing Hormone (TRH). The release of TRH tells the pituitary gland to release something called Thyroid Stimulating Hormone (TSH). This TSH, circulating in your bloodstream, is what tells the thyroid to make thyroid hormones and release them into your bloodstream.

What Causes Thyroid Disease?

What causes thyroid problems? Besides the treatments mentioned above, there are other factors that can contribute to the development of various thyroid problems:
  • Exposure to radiation, such as occurred after the Chernobyl nuclear plant accident
  • Overconsumption of isoflavone-intensive soy products, such as soy protein, soy capsules, soy powders
  • Some drugs, such as lithium and the heart drug cordarone, can cause hypothyroidism.
  • An overconsumption or shortage of iodine in the diet can also trigger some thyroid problems. (This also applies to iodine-containing supplements, such as kelp and bladderwrack.)
  • Radiation treatment to my head, neck or chest. Radiation treatment for tonsils, adenoids, lymph nodes, thymus gland problems, or acne
  • "Nasal Radium Therapy," which took place during the 1940s through 1960s, as a treatment for tonsillitis, colds and other ailments, or as a military submariner and/or pilot who had trouble with drastic changes in pressure
  • Overconsumption of uncooked "goitrogenic" foods, such as brussels sprouts, broccoli, rutabaga, turnips, kohlrabi, radishes, cauliflower, African cassava, millet, babassu (a palm-tree coconut fruit popular in Brazil and Africa), cabbage and kale
You have a higher risk of developing thyroid disease if:

…You have a family member with a thyroid problem
…You have another pituitary or endocrine disease
…You or a family member have another autoimmune disease
…You've been diagnosed with Chronic Fatigue Syndrome
…You've been diagnosed with Fibromyalgia
…You're female
…You're over 60
…You've just had a baby
…You're near menopause or menopausal
…You're a smoker
…You've been exposed to radiation
…You've been treated with lithium
…You eat too much soy foods
…You've been exposed to certain chemicals (i.e., perchlorate, fluoride)

What is Hypothyroidism?

Most people with thyroid disease end up hypothyroid, the situation where the thyroid is either underactive, totally unable to function, or has been surgically removed. The most common cause of hypothyroidism is an autoimmune condition known as Hashimoto's Thyroiditis, in which antibodies begin to attack the thyroid and gradually make it inactive. Treatment for hyperthyroidism also usually results in hypothyroidism. Radioactive Iodine (RAI) treatment, and surgical removal of the thyroid to treat an overactive thyroid usually ends up leaving a patient hypothyroid. Some people need to have the thyroid partially or fully removed -- known as thyroidectomy -- due to nodules/lumps in the thyroid. This can leave you hypothyroid. And the treatment for thyroid cancer is usually surgical removal of the thyroid. Bottom line: your thyroid doesn't produce enough thyroid hormone, or you don't have a thyroid at all -- and you are considered hypothyroid.

The symptoms of hypothyroidism depend on how hypothyroid you are, your age, your general level of health, and how hypothyroidism affects you uniquely. You may have some or all of the following symptoms, in varying severity:
  • You feel tired, exhausted, and like you can't get enough sleep, or want to take daytime naps
  • You feel depressed, down, or sad
  • You feel cold when others do not, particularly in hands and feet
  • You've gained weight inappropriately, or you are finding it difficult to lose weight, despite proper diet and exercise
  • You're losing hair, particularly from the outer part of your eyebrow, or your hair is getting dry, or tangly
  • Your nails are breaking and splitting and become brittle
  • You've been diagnosed as having chronic fatigue syndrome
  • You have You have muscle and joint pains and aches, or you've been diagnosed with fibromyalgia, carpal tunnel syndrome, or tendonitis in arms and legs
  • You have swelling and puffiness in the eyes, face, arms or legs
  • You have a low low sex drive
  • You have heart palpitations or a diagnosis of mitral valve prolapse
  • You're suffering from unexplained infertility, or have had recurrent miscarriages with no obvious explanation
  • You have had a heart attack or have clogged arteries
  • You have high cholesterol levels, particularly the type that is unresponsive to diet and medication
  • You have a heavier than normal menstrual period, or your period is longer than it used to be, or comes more frequently
  • You're going through menopause, and are having troublesome symptoms
  • You have worsening allergies, itching, prickly hot skin, rashes, hives, urticaria, chronic yeast infections, oral fungus or thrush, or stomach and abdominal bloating
  • You have anemia, or an excess of iron known as hemachromatosis
  • You find it difficult to concentrate, your memory is not as good as it should be, you feel like your thinking is "slow"
  • You are constipated, sometimes severely so
  • You have a feeling of fullness, or an obvious swelling in your neck area For many of you, if you have not had surgery or radiation treatment that is an obvious cause of your hypothyroidism, the doctor may dismiss your symptoms, suggesting instead that you are suffering from depression, not enough sleep, a need for exercise, or simply the effects of stress. For women, you might be told these are the symptoms of premenstrual syndrome or menopause or normal post-partum problems.

    The reality is that symptoms such as fatigue, anxiety, unexplained weight gain, hair loss, and depression, may indicate that you have undiagnosed hypothyroidism.

    How do you know if you have hypothyroidism, the most commonly diagnosed thyroid problem? Start with a careful review of the above symptoms, and to help, you can download and print out our comprehensive Hypothyroidism Symptoms Checklist.

    If your doctor suspects hypothyroidism, he or she will order a TSH (thyroid stimulating hormone) test. Most American laboratories have a normal range from around .5 to 5.5. A TSH level above 5.5 or 6 is usually diagnosed as hypothyroid.

    However, there are doctors who believe that you do not need to have an elevated TSH level in order to actually be diagnosed and treated for hypothyroidism. Increasingly, innovative doctors are also viewing high-normal or normal TSH levels as possible evidence of low-level hypothyroidism. Dr. John Dommisse, in an interview with Mary Shomon, has said that that "The so-called 'normal range' is way too high"

    Elizabeth Lee Vliet, M.D. is author of Screaming to Be Heard: Hormonal Connections Women Suspect...and Doctors Ignore, does not tell her patients their thyroids are normal based only on TSH results. According to Vliet, "The normal range is relative. Many women have symptoms -- or are hypothyroid -- when TSH is anywhere but the lower end of the range."

    Dr. Vliet also tests for elevated thyroid antibodies, and low Free T3 and Free T4 levels. "Most women with elevated antibodies are in the process of developing autoimmune thyroid disease," says Vliet. "And even with normal TSH levels, I've found that majority of women with elevated antibodies, low Free T3 and low Free T4 require thyroid hormone replacement to feel well."

    Doctors usually prescribe the synthetic T4 hormone levothyroxine to treat hypothyroidism. Popular brands include Levoxyl and Synthroid. Research reported in the New England Journal of Medicine in February of 1999 found that a majority of patients may feel better on a combination of hormones. On that basis of that study, more doctors are also adding synthetic T3 (liothyronine). Alternative physicians tend to prefer Thyrolar, Armour, or Naturethroid, drugs that include both hormones.

    What is Hyperthyroidism?

    When your thyroid starts producing too much thyroid hormone and the balancing system doesn't function properly, then you can become hyperthyroid, and your body goes into overdrive, gets sped up, causing an increased heart rate, increased blood pressure, and burning more calories more quickly.

    Several years ago, Olympic medal-winning athlete Gail Devers testified before Congress regarding her own case of Graves' disease, an autoimmune condition that can cause hyperthyroidism. In Devers' case, doctor after doctor failed to recognize the signs of severe Graves' disease, as the Olympic gold medal-winning athlete dropped from 125 to only 87 pounds, suffered debilitating fatigue, lost nearly all her hair, and suffered other symptoms including rapid heart rate, and dry skin. It was two years before Devers was finally diagnosed and treated.

    If you're hyperthyroid, you may find:
    • You're rapidly losing weight, or you are eating more and not gaining weight
    • You're having a hard time falling asleep or staying asleep, or you have insomnia
    • You're suffering from anxiety, irritability, nervousness, or even panic attacks
    • You're having palpitations, or your pulse and heartbeat are fast
    • You're sweating more than usual, feeling hot when others are not
    • You have tremors in your hands
    • You're suffering from diarrhea
    • You feel tired
    • Your skin is dry, or you may even have a thickening of the skin on the shin area of your legs
    • Your periods are stopped, or very light, or infrequent
    • You're having muscle weakness, especially in the upper arms and thighs
    • You're having eye problems, such as double vision, scratchy eyes, or you notice that your eyes are bulging or more whites are showing than usual
    • You're having trouble getting pregnant
    • Your hair has become fine and brittle
    • You're having a hard time concentrating, your attention span is short
    • Your behavior is erratic
    Your doctor will typically run a TSH blood test, and will look for low -- below .5 to nearly undetectable -- TSH levels to diagnose hyperthyroidism.

    If you have a milder case of hyperthyroidism, your doctor may initially prescribe antithyroid drugs such as methimazole (Tapazole) or propylthiouracil (PTU), as these drugs offer some chance of a remission. For more advanced hyperthyroidism, doctors prefer radioactive iodine treatment, known as RAI. By partially or fully disabling the thyroid, RAI eliminates hormone overproduction, but commonly results in life-long hypothyroidism. Surgery, known as thyroidectomy, is typically only done when you cannot tolerate antithyroid drugs, or are not a good candidate for RAI.

    A comprehensive and detailed look at hyperthyroidism diagnosis, treatment and options is covered in our
    Graves' Disease/Hyperthyroidism FAQ.

    Alternative treatment for hyperthyroidism and Graves' Disease is considered controversial, but it's becoming more widespread. Read all about it in this interview with author Elaine Moore, at Graves' Disease A Practical Guide

    What is a Goiter? What is a Thyroid Nodule?

    Sometimes, when the thyroid is hypothyroid or hyperthyroid, it can become enlarged. Then the enlarged thyroid is called a "goiter." Some goiters will return to normal with proper hypothyroidism or hyerthyroidism treatment. In some cases, however, goiters may be surgically removed for cosmetic reasons, or because they are making breathing or swallowing difficult.

    The thyroid can also occasionally develop lumps and cysts, known as nodules. Most of these are benign, and it's estimated that anywhere from 10 to 50% of the population have a thyroid nodule at any one time. The overwhelming majority of all nodules are benign. Occasionally, a nodule may be suspicious and suggestive of cancer. Nodules are typically evaluated by ultrasound scan and blood tests, and sometimes by an outpatient biopsy called fine needle aspiration (FNA). The vast majority of nodules are benign, and some are treated with levothyroxine. If cancer can't be ruled out, or your thyroid is obstructing breathing or swallowing, your doctor will likely recommend surgery.

    What is Thyroid Cancer?

    Malignant tumors of the thyroid -- thyroid cancer -- are not common. Thyroid cancer accounts for only 1.2% of all new cancers (outside skin cancers) in the United States annually. In the U.S., about 14,000 new cases are diagnosed each year. There are four types of thyroid cancer:
    • About 75% of Thyroid Cancers are Papillary and Papillary/follicular
    • About 15% are Follicular and Hurthle cell
    • About 7% are Medullary
    • About 3% are Anaplastic
    Most thyroid cancers are very curable and the most common types of thyroid cancer -- papillary and follicular -- are the most highly curable. In most cases, a thyroid cancer is diagnosed from evaluation of a nodule. Only a small percentage -- less than 5% -- of nodules are cancerous.

    Both papillary and follicular cancers are typically treated with complete removal of the lobe of the thyroid which harbors the cancer, PLUS, removal of most or all of the other side.

    Typically, chemotherapy and radiation are not usually done for thyroid cancer.
    Surgery is performed to remove the thyroid, and any affected lymph nodes. Then, thyroid cells' unique ability to absorb iodine, which no other organ or cell can do, means that radioactive iodine treatment can be administered as a way to target radiation solely at the cancerous thyroid cells. In the case of certain types of thyroid cancer, and with very small papillary cancers, some patients are treated only with surgery.

    More information on thyroid cancer is available here at the website, or from the Thyroid Cancer Survivors' Association.

    Can You Prevent Thyroid Disease?

    There are several things you can do to reduce your chance of thyroid problems.

    Be Careful About Too Much Soy
    There's evidence that excessive isoflavones -- found in popular soy products and supplements --
    may cause hypothyroidism, goiter or nodules. Larrian Gillespie, M.D., author of The Goddess Diet, says "one serving of tofu a day is all you need to enjoy soy's benefits. Going overboard on soy supplements and powders may trigger or worsen thyroid problems." Also, remember that a long-term, steady diet of soy formula may make your baby more vulnerable to developing autoimmune thyroid conditions, due to overexposure to antithyroid isoflavones.

    Drink Bottled Water
    Fluoride in water, and a rocket fuel manufacturing by-product known as perchlorate, and other toxic chemicals are among the many substances in water that may trigger or worsen the risk of thyroid problems. Consider drinking purified or bottled water.

    When It Comes to Iodine -- Think Moderation
    Too little iodine, an increasing problem in the United States, increases your risk of hypothyroidism or goiter, but excessive iodine intake -- including kelp or bladderwrack -- can also affect the thyroid.

    Stop Smoking
    Smoking can damage the thyroid, and actually worsens some existing thyroid conditions . . . yet another reason to quit -- or never start -- smoking.

    Reduce Your Stress
    Reducing stress using effective techniques such as aerobic exercise, yoga and mind-body techniques can play a part in preventing some autoimmune problems like thyroid disease.

    Return to Endocrine Information Center Index

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