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What is hyperthyroidism?
The term hyperthyroidism refers to any condition in which there is too much thyroid hormone in the body. In other words, the thyroid gland is overactive.


What are the symptoms of hyperthyroidism?
Thyroid hormone generally controls the pace of all of the processes in the body. This pace is called your metabolism. If there is too much thyroid hormone, every function of the body tends to speed up. It is not surprising then that some of the symptoms of hyperthyroidism are nervousness, irritability, increased perspiration, heart racing, hand tremors, anxiety, difficulty sleeping, thinning of your skin, fine brittle hair, and muscular weakness-especially in the upper arms and thighs. You may have more frequent bowel movements, but diarrhea is uncommon. You may lose weight despite a good appetite and, for women, menstrual flow may lighten and menstrual periods may occur less often.

Hyperthyroidism usually begins slowly. At first, the symptoms may be mistaken for simple nervousness due to stress. If you have been trying to lose weight by dieting, you may be pleased with your success until the hyperthyroidism, which has quickened the weight loss, causes other problems.

In Graves' disease, which is the most common form of hyperthyroidism, the eyes may look enlarged because the upper lids are elevated. Sometimes, one or both eyes may bulge. Some patients have swelling of the front of the neck from an enlarged thyroid gland (a goiter).


What causes hyperthyroidism?
The most common cause (in more than 70% of people) is overproduction of thyroid hormone by the entire thyroid gland. This condition is also known as Graves' disease (see the Graves' Disease brochurefor details). Graves' disease is caused by antibodies in the blood that stimulate the thyroid to grow and secrete too much thyroid hormone. This type of hyperthyroidism tends to run in families, and it occurs more often in young women. Little is known about why specific individuals get this disease. Another type of hyperthyroidism is characterized by one or more nodules or lumps in the thyroid that may gradually grow and increase their activity so that the total output of thyroid hormone into the blood is greater than normal. This condition is known as toxic nodular or multinodular goiter. Also, people may temporarily have symptoms of hyperthyroidism if they have a condition called thyroiditis. This condition is caused by a problem with the immune system or a viral infection that causes the gland to leak thyroid hormone. It can also be caused by taking too much thyroid hormone in tablet form.


How is hyperthyroidism diagnosed?
If your physician suspects that you have hyperthyroidism, diagnosis is usually a simple matter. A physical examination usually detects an enlarged thyroid gland and a rapid pulse. The physician will also look for moist, smooth skin and a tremor of your fingertips. Your reflexes are likely to be fast, and your eyes may have some abnormalities if you have Graves' disease.

The diagnosis of hyperthyroidism will be confirmed by laboratory tests that measure the amount of thyroid hormones- thyroxine (T4) and triiodothyronine (T3)-and thyroid-stimulating hormone (TSH) in your blood. A high level of thyroid hormone in the blood plus a low level of TSH is common with an overactive thyroid gland. If blood tests show that your thyroid is overactive, your doctor may want to obtain a picture of your thyroid (a thyroid scan). The scan will find out if your entire thyroid gland is overactive or whether you have a toxic nodular goiter or thyroiditis (thyroid inflammation). A test that measures the ability of the gland to collect iodine may be done at the same time.


How is hyperthyroidism treated?
No single treatment is best for all patients with hyperthyroidism. Your doctor's choice of treatment will be influenced by your age, the type of hyperthyroidism that you have, the severity of your hyperthyroidism, and other medical conditions that may be affecting your health. It may be a good idea to consult with a physician who is experienced in the treatment of hyperthyroid patients. If you are unconvinced or unclear about any thyroid treatment plan, a second opinion is a good idea.

Antithyroid drugs
Drugs known as antithyroid agents-methimazole (Tapazole®) or propylthiouracil (PTU)-may be prescribed if your doctor chooses to treat the hyperthyroidism by blocking the thyroid gland's ability to make new thyroid hormone. These drugs work well to control the overactive thyroid, bring prompt control of hyperthyroidism, and do not cause permanent damage to the thyroid gland. In about 20% to 30% of patients with Graves' disease, treatment with antithyroid drugs for a period of 12 to 18 months will result in prolonged remission of the disease. For patients with toxic nodular or multinodular goiter, antithyroid drugs are used in preparation for either radioiodine treatment or surgery. Antithyroid drugs cause allergic reactions in about 5% of patients who take them. Common minor reactions are red skin rashes, hives, and occasionally fever and joint pains. A rarer (occurring in 1 of 500 patients), but more serious side effect is a decrease in the number of white blood cells. Such a decrease can lower your resistance to infection. Very rarely, these white blood cells disappear completely, producing a condition known as agranulocytosis, a potentially fatal problem if a serious infection occurs. If you are taking one of these drugs and get an infection such as a fever or sore throat, you should stop the drug immediately and have a white blood cell count that day. Even if the drug has lowered your white blood cell count, the count will return to normal if the drug is stopped immediately. But if you continue to take one of these drugs in spite of a low white blood cell count, there is a risk of a more serious, even life-threatening infection. Liver damage is another very rare side effect. You should stop the drug and call your doctor if you develop yellow eyes, dark urine, severe fatigue, or abdominal pain.

Radioactive iodine
Another way to treat hyperthyroidism is to damage or destroy the thyroid cells that make thyroid hormone. Because these cells need iodine to make thyroid hormone, they will take up any form of iodine in your blood stream, whether it is radioactive or not. The radioactive iodine used in this treatment is administered by mouth, usually in a small capsule that is taken just once. Once swallowed, the radioiodine gets into your blood stream and quickly is taken up by the overactive thyroid cells. The radioiodine that is not taken up by the thyroid cells disappears from the body within days. It is either eliminated in the urine or transformed by radioactive decay into a nonradioactive state. Over a period of several weeks to several months (during which time drug treatment may be used to control hyperthyroid symptoms), radioactive iodine damages the cells that have taken it up. The result is that the thyroid or thyroid nodules shrink in size, and the level of thyroid hormone in the blood returns to normal. Sometimes patients will remain hyperthyroid, but usually to a lesser degree than before. For them, a second radioiodine treatment can be given if needed. More often, hypothyroidism (an underactive thyroid) occurs after a few months. In fact, most patients treated with radioactive iodine will become hypothyroid after a period of several months to many years. Hypothyroidism can easily be treated with a thyroid hormone supplement taken once a day (see theHypothyroidism brochure).

Radioactive iodine has been used to treat patients for hyperthyroidism for over 60 years. Because of concern that the radioactive iodine might somehow damage other cells in the body, produce cancer, or have other long-term unwanted effects such as infertility or birth defects, the physicians who first used radioiodine treatments were careful to treat only adults and to observe them carefully for the rest of their lives. Fortunately, no complications from radioiodine treatment have become apparent over many decades of careful follow-up of patients. As a result, in the United States more than 70% of adults who develop hyperthyroidism are treated with radioactive iodine. More and more children are also being treated with radioiodine.

Your hyperthyroidism can be permanently cured by surgical removal of most of your thyroid gland. This procedure is best performed by a surgeon who has much experience in thyroid surgery. An operation could be risky unless your hyperthyroidism is first controlled by an antithyroid drug (see above) or a beta-blocking drug (see below). Usually for some days before surgery, your surgeon may want you to take drops of nonradioactive iodine-either Lugol's iodine or supersaturated potassium iodide (SSKI). This extra iodine reduces the blood supply to the thyroid gland and thus makes the surgery easier and safer. Although any surgery is risky, major complications of thyroid surgery occur in less than 1% of patients operated on by an experienced thyroid surgeon. These complications include damage to the parathyroid glands that surround the thyroid and control your body's calcium levels (causing problems with low calcium levels) and damage to the nerves that control your vocal cords (causing you to have a hoarse voice).

After your thyroid gland is removed, the source of your hyperthyroidism is gone and you will likely become hypothyroid. As with hypothyroidism that develops after radioiodine treatment, your thyroid hormone levels can be restored to normal by treatment once a day with a thyroid hormone supplement.

No matter which of these three methods of treatment you have for your hyperthyroidism, your physician may prescribe a class of drugs known as the beta adrenergic blocking agents that block the action of thyroid hormone on your body. They usually make you feel better within hours, even though they do not change the high levels of thyroid hormone in your blood. These drugs may be extremely helpful in slowing down your heart rate and reducing the symptoms of palpitations, shakes, and nervousness until one of the other forms of treatment has a chance to take effect. Propranolol (Inderal®) was the first of these drugs to be developed. Some physicians now prefer related, but longer-acting betablocking drugs such as atenolol (Tenormin®), metoprolol (Lopressor®) and nadolol (Corgard®), and Inderal-LA® because of their more convenient once- or twice-a-day dosage.

Other family members at risk
Because hyperthyroidism, especially Graves' disease, may run in families, examinations of the members of your family may reveal other individuals with thyroid problems.


What is hypothyroidism?
Hypothyroidism is an underactive thyroid gland. Hypothyroidism means that the thyroid gland can't make enough thyroid hormone to keep the body running normally. People are hypothyroid if they have too little thyroid hormone in the blood. Common causes are autoimmune disease, surgical removal of the thyroid, and radiation treatment.


What are the symptoms?
When thyroid hormone levels are too low, the body's cells can't get enough thyroid hormone and the body's processes start slowing down. As the body slows, you may notice that you feel colder, you tire more easily, your skin is getting drier, you're becoming forgetful and depressed, and you've started getting constipated. Because the symptoms are so variable, the only way to know for sure whether you have hypothyroidism is with blood tests.

Keeping other people informed. Tell your family members. Because thyroid disease runs in families, you should explain your hypothyroidism to your relatives and encourage them to get regular TSH tests. Tell your other doctors and your pharmacist about your hypothyroidism and the drug and dose with which it is being treated. If you start seeing a new doctor, tell the doctor that you have hypothyroidism and you need your TSH tested every year. If you are seeing an endocrinologist, ask that copies of your reports be sent to your primary care doctor.

What can you expect over the long term?
There is no cure for hypothyroidism, and most patients have it for life. There are exceptions: many patients with viral thyroiditis have their thyroid function return to normal, as do some patients with thyroiditis after pregnancy.

Hypothyroidism may become more or less severe, and your dose of thyroxine may need to change over time. You have to make a lifetime commitment to treatment. But if you take your pills every day and work with your doctor to get and keep your thyroxine dose right, you should be able to keep your hypothyroidism completely controlled throughout your life.Your symptoms should disappear and the serious effects of low thyroid hormone should stop getting worse and should actually improve. If you keep your hypothyroidism well-controlled, it will not shorten your life span.


What causes hypothyroidism?
There can be many reasons why the cells in the thyroid gland can't make enough thyroid hormone. Here are the major causes, from the most to the least common.

  • Autoimmune disease. In some people's bodies, the immune system that protects the body from invading infections can mistake thyroid gland cells and their enzymes for invaders and can attack them. Then there aren't enough thyroid cells and enzymes left to make enough thyroid hormone. This is more common in women than men. Autoimmune thyroiditis can begin suddenly or it can develop slowly over years. The most common forms are Hashimoto's thyroiditis and atrophic thyroiditis.

  • Surgical removal of part or all of the thyroid gland. Some people with thyroid nodules, thyroid cancer, or Graves' disease need to have part or all of their thyroid removed. If the whole thyroid is removed, people will definitely become hypothyroid. If part of the gland is left, it may be able to make enough thyroid hormone to keep blood levels normal.

  • Radiation treatment. Some people with Graves' disease, nodular goiter, or thyroid cancer are treated with radioactive iodine (I-131) for the purpose of destroying their thyroid gland. Patients with Hodgkin's disease, lymphoma, or cancers of the head or neck are treated with radiation. All these patients can lose part or all of their thyroid function.

  • Congenital hypothyroidism (hypothyroidism that a baby is born with). A few babies are born without a thyroid or with only a partly formed one. A few have part or all of their thyroid in the wrong place (ectopic thyroid). In some babies, the thyroid cells or their enzymes don't work right.

  • Thyroiditis. Thyroiditis is an inflammation of the thyroid gland, usually caused by an autoimmune attack or by a viral infection. Thyroiditis can make the thyroid dump its whole supply of stored thyroid hormone into the blood at once, causing brief HYPERthyroidism (too much thyroid activity); then the thyroid becomes underactive.

  • Medicines. Medicines such as amiodarone, lithium, interferon alpha, and interleukin-2 can prevent the thyroid gland from being able to make hormone normally. These drugs are most likely to trigger hypothyroidism in patients who have a genetic tendency to autoimmune thyroid disease.

  • Too much or too little iodine.The thyroid gland must have iodine to make thyroid hormone. Iodine comes into the body in food and travels through the blood to the thyroid. Keeping thyroid hormone production in balance requires the right amount of iodine. Taking in too much iodine can cause or worsen hypothyroidism.

  • Damage to the pituitary gland. The pituitary, the "master gland," tells the thyroid how much hormone to make. When the pituitary is damaged by a tumor, radiation, or surgery, it may no longer be able to give the thyroid instructions, and the thyroid may stop making enough hormone.

  • Rare disorders that infiltrate the thyroid. In a few people, diseases deposit abnormal substances in the thyroid. For example, amyloidosis can deposit amyloid protein, sarcoidosis can deposit granulomas, and hemochromatosis can deposit iron.


How is hypothyroidism diagnosed?
The correct diagnosis of hypothyroidism depends on the following.

  • Symptoms. Hypothyroidism doesn't have any characteristic symptoms. There are no symptoms that people with hypothyroidism always have but that no one with another disease ever has. One way to help figure out whether your complaints are symptoms of hypothyroidism is to think about whether you've always had a symptom (hypothyroidism is less likely) or whether the symptom is a change from the way you used to feel (hypothyroidism is more likely).

  • Medical and family history. You should tell your doctor:
    • about changes in your health that suggest that your body is slowing down;
    • if you've ever had thyroid surgery;
    • if you've ever had radiation to your neck to treat cancer;
    • if you're taking any of the medicines that can cause hypothyroidism- amiodarone, lithium, interferon alpha, interleukin- 2, and maybe thalidomide;
    • whether any of your family members have thyroid disease.

  • Physical exam. The doctor will check your thyroid gland and look for changes such as dry skin, swelling, slower reflexes, and a slower heart rate.

  • Blood tests. There are two blood tests that are used in the diagnosis of hypothyroidism.

    TSH (thyroid-stimulating hormone) test. This is the most important and sensitive test for hypothyroidism. It measures how much of the thyroid hormone thyroxine (T4) the thyroid gland is being asked to make. An abnormally high TSH means hypothyroidism: the thyroid gland is being asked to make more T4 because there isn't enough T4 in the blood.

    T4 tests. Most of the T4 in the blood is attached to a protein called thyroxine-binding globulin. The "bound" T4 can't get into body cells. Only about 1%-2% of T4 in the blood is unattached ("free") and can get into cells. The free T4 and the free T4 index are both simple blood tests that measure how much unattached T4 is in the blood and available to get into cells.


How is hypothyroidism treated?

Thyroxine (T4) replacement.
Hypothyroidism can't be cured. But in almost every patient, hypothyroidism can be completely controlled. It is treated by replacing the amount of hormone that your own thyroid can no longer make, to bring your T4 and TSH back to normal levels. So even if your thyroid gland can't work right, T4 replacement can restore your body's thyroid hormone levels and your body's function. Synthetic thyroxine pills contain hormone exactly like the T4 that the thyroid gland itself makes. All hypothyroid patients except those with severe myxedema can be treated as outpatients, not having to be admitted to the hospital.

Side effects and complications. The only dangers of thyroxine are caused by taking too little or too much. If you take too little, your hypothyroidism will continue. If you take too much, you'll develop the symptoms of hyperthyroidism-an overactive thyroid gland. The most common symptoms of too much thyroid hormone are fatigue but inability to sleep, greater appetite, nervousness, shakiness, feeling hot when other people are cold, and trouble exercising because of weak muscles, shortness of breath , and a racing, skipping heart. Patients who have hyperthyroid symptoms should have their TSH tested. If it is low, indicating too much thyroid hormone, their dose may need to be lowered.

You'll need to have your TSH checked about every 6 to 10 weeks after a thyroxine dose change. You may need tests more often if you're pregnant or you're taking a medicine that interferes with your body's ability to use thyroxine. The goal of treatment is to get and keep your TSH in the normal range. Babies must get all their daily treatments and have their TSH levels checked as they grow, to prevent mental retardation and stunted growth. Once you've settled into a thyroxine dose, you can return for TSH tests only about once a year. You need to return sooner if any of the following apply to you:

  • Your symptoms return or get worse.

  • You want to change your thyroxine dose or brand, or change taking your pills with or without food.

  • You gain or lose a lot of weight (as little as a 10-pound difference for those who weren't overweight to begin with).

  • You start or stop taking a drug that can interfere with absorbing thyroxine, or you change your dose of such a drug.

  • You're not taking all your thyroxine pills. Tell your doctor honestly how many pills you've missed.

  • You want to try stopping thyroxine treatment. If ever you think you're doing well enough not to need thyroxine treatment any longer, try it only under your doctor's close supervision. Rather than stopping your pills completely, you might ask your doctor to try lowering your dose. If your TSH goes up, you'll know that you need to continue treatment.


Iodine Deficiency

What is iodine deficiency?
Iodine is an element that is needed for the production of thyroid hormone. The body does not make iodine, so it is an essential part of your diet. Iodine is found in various foods (see Table 1 below). If you do not have enough iodine in your body, you cannot make enough thyroid hormone. Thus, iodine deficiency can lead to enlargement of the thyroid (goiter - see Goiter brochure), hypothyroidism (see Hypothyroidism brochure) and to mental retardation in infants and children whose mothers were iodine deficient during pregnancy.

Before the 1920s, iodine deficiency was common in the Great Lakes, Appalachian, and Northwestern U.S. regions and in most of Canada. Treatment of iodine deficiency by the introduction of iodized salt has virtually eliminated the "goiter belt" in these areas. However, many other parts of the world do not have enough iodine available through their diet and iodine deficiency continues to be an important public health problem globally. Approximately 40% of the world's population remains at risk for iodine deficiency.


What are the symptoms of iodine deficiency?
All of the symptoms of iodine deficiency are related to its effect on the thyroid:

Goiter - Without adequate iodine, the thyroid progressively enlarges (develops a goiter) as it tries to keep up with demand for thyroid hormone production. Worldwide, iodine deficiency is the most common cause of thyroid enlargement and goiter (see Goiter brochure). Within a goiter, nodules can develop. Patients with a large goiter may experience symptoms of choking, especially when lying down, and difficulty swallowing and breathing.

Hypothyroidism - As the body's iodine levels fall, hypothyroidism may develop, since iodine is essential for making thyroid hormone. While this is uncommon in the United States, iodine deficiency is the most common cause of hypothyroidism worldwide (see Hypothyroidism brochure).

Pregnancy-related problems - Iodine deficiency is especially important in women who are pregnant or nursing their infants. Severe iodine deficiency in the mother has been associated with miscarriages, stillbirth, preterm delivery, and congenital abnormalities in their babies. Children of mothers with severe iodine deficiency during pregnancy can have mental retardation and problems with growth, hearing, and speech. In the most severe form, an underactive thyroid can result in cretinism (a syndrome characterized by permanent brain damage, mental retardation, deaf mutism, spasticity, and short stature), though this is not seen in the United States. Congenital hypothyroidism due to iodine deficiency is the most common preventable cause of mental retardation in the world. Even mild iodine deficiency during pregnancy, which may be present in some women in the United States, may be associated with low intelligence in children.


What are the causes of iodine iodine deficiency?
Since the body does not make iodine, it relies on the diet to have enough iodine. Thus, iodine deficiency is caused but not having enough iodine in the diet. Iodine is present naturally in soil and seawater. The availability of iodine in foods differs in various regions of the world (see Table 1). Individuals in the United States can maintain adequate iodine in their diet by using iodized table salt (unless they have to restrict the amount of salt in their diet), by eating foods high in iodine, particularly dairy products, seafood, meat, some breads, and eggs, and by taking a multivitamin containing iodine (see below). However, the amount of iodine in foods is not listed on food packaging in the U.S., and it can be difficult to identify sources of iodine in foods.


How do you diagnose iodine deficiency?
Iodine deficiency is diagnosed across populations and not specifically in individuals. Since iodine is released from the body through the urine, the best way to determine iodine deficiency across a large population is to measure the amounts of iodine in urine samples. Iodine deficiency is defined as a median urinary iodine concentration less than 50 μg/L in a population (see Table 2).

In the United States, iodine status has remained generally adequate in the last 2 decades although studies have shown that urinary iodine levels dropped by about half between the early 1970s and the early 1990s. However, iodine deficiency is a major issue in other parts of the world, including parts of Europe, Africa and Asia.


How is iodine deficiency treated?
There are no tests to confirm if you have enough iodine in your body. When iodine deficiency is seen in an entire population, it is best managed by ensuring that common foods that people eat contain sufficient levels of iodine. Since even mild deficiency during pregnancy can have effects on delivery and the developing baby, all pregnant and breastfeeding women should take a multivitamin containing at least 150 μg iodine per day.

How is iodine deficiency prevented?
As with many diseases, it is better to prevent the problem rather than have to treat it. Over the last 80 years, world-wide efforts have been made to eliminate iodine deficiency. Indeed, elimination of iodine deficiency has been a major goal of the World Health Organization. Iodized salt has been the mainstay of treatment for iodine deficiency worldwide, including in the United States. Injections of iodized oil are occasionally used in regions of the world where widespread iodized salt use is not possible. Iodination of water supplies also has been effective in some places.

United States Recommendations - The Institute of Medicine has set the Recommended Dietary Allowance (RDA) for iodine in adult men and women at 150 μg per day. Individuals who add table salt to their food regularly should use iodized salt. One teaspoon of iodized salt contains approximately 400 μg iodine. Most iodine-containing multivitamins have at least 150 μg iodine, but only about half of the types of multivitamins in the U.S. contain iodine.

The RDA is 220 μg iodine per day for pregnant women and 290 μg iodine per day for breastfeeding women. Because the effects of iodine deficiency are most severe in pregnant women and their babies, the American Thyroid Association has recommended that all pregnant and breastfeeding women in the U.S. and Canada take a prenatal multivitamin containing 150 μg iodine per day.

Are there problems with taking too much iodine?
Taking too much iodine can also cause problems. This is especially true in individuals that already have thyroid problems, such as nodules, hyperthyroidism and autoimmune thyroid disease. Administration of large amounts of iodine through medications (ie Amiodarone), radiology procedures (iodinated intravenous dye) and dietary excess (Dulce, kelp) can cause or worsen hyperthyroidism and hypothyroidism.

In addition, individuals who move from an iodine-deficient region (for example, parts of Europe) to a region with adequate iodine intake (for example, the United States) may also develop thyroid problems since their thyroids have become very good at taking up and using small amounts of iodine. In particular, these patients may develop iodine-induced hyperthyroidism (see Hyperthyroidism brochure).

Graves' Disease

What is Graves' disease?
Graves' disease, a type of hyperthyroidism, is caused by a generalized overactivity of the entire thyroid gland. It is named for Robert Graves, an Irish physician, who was the first to describe this form of hyperthyroidism about 150 years ago.


What are the symptoms of Graves' disease?

  • Hyperthyroidism
    The hyperthyroid symptoms of Graves' disease are often the same as those caused by other types of hyperthyroidism (see the Hyperthyroidism brochure).

  • Eye disease
    Graves' disease is the only kind of hyperthyroidism that has inflammation of the eyes, swelling of the tissues around the eyes, and bulging of the eyes (called Graves'ophthalmopathy). The cause of these problems is unknown. Although many patients with Graves' disease have redness and irritation of the eyes at some time, less than 1% ever develop enough inflammation of the eye tissues to cause serious or permanent trouble. Patients who have severe eye symptoms may benefit from visiting an eye doctor (an ophthalmologist).

    Eye symptoms generally begin about 6 months before or after the diagnosis of Graves' disease has been made. Seldom do eye problems occur long after the disease has been treated. In some patients with eye symptoms, hyperthyroidism never develops. The severity of the eye problems is not related to the severity of the hyperthyroidism. Early signs of trouble might be red or inflamed eyes or a bulging of the eyes due to inflammation of the tissues behind the eyeball. Diminished or double vision are rare problems that usually occur later. We do not know why, but problems with the eyes occur much more often in people with Graves' disease who smoke cigarettes than in those who don't smoke.

  • Skin disease
    Rarely, patients with Graves' disease develop a lumpy reddish thickening of the skin in front of the shins known as pretibial myxedema. This skin condition is usually painless and is not serious. Like the eye trouble of Graves' disease, the skin problem does not necessarily begin precisely when the hyperthyroidism starts. Its severity is not related to the level of thyroid hormone. We don't know why this problem is usually limited to the lower leg or why so few people have it.


What causes Graves' disease?
Graves' disease is triggered by some process in the body's immune system, which normally protects us from foreign invaders such as bacteria and viruses. The immune system destroys foreign invaders with substances called antibodies produced by blood cells known as lymphocytes. Many people inherit an immune system that can cause problems. Their lymphocytes make antibodies against their own tissues that stimulate or damage them. In Graves' disease, antibodies bind to the surface of thyroid cells and stimulate those cells to overproduce thyroid hormones. This results in an overactive thyroid. Physicians have long suspected that severe emotional stress, such as the death of a loved one, can set off Graves' disease in some patients. Dr. Graves himself commented on stressful events in his patients' lives that came several months before the development of hyperthyroidism. However, many patients who develop Graves' disease report no stress in their lives.


How is the diagnosis of Graves' disease made?
The diagnosis of hyperthyroidism is made on the basis of findings during a physical exam and confirmed by laboratory tests that measure the amount of thyroid hormone (thyroxine, or T4, and triiodothyronine, or T3) and thyroid-stimulating hormone (TSH) in your blood (see the Hyperthyroidism brochure). Sometimes your doctor may want you to have a radioactive image, or scan, of the thyroid to see whether the entire thyroid gland is overactive. Your doctor may also wish to do a blood test to confirm the presence of thyroid-stimulating antibodies (TSAb) that cause Graves' disease, but this test is not usually necessary.

Clues that your hyperthyroidism is caused by Graves' disease are the presence of Graves' eye disease (see above), an enlarged thyroid, and a history of other family members with thyroid problems. Some relatives may have had hyperthyroidism or an underactive thyroid; others may have acquired gray hair prematurely (beginning in their 20's). Similarly, there may be a history of related immune problems in the family, including juvenile diabetes, pernicious anemia (due to lack of vitamin B12), or painless white patches on the skin known as vitiligo


How is Graves' disease treated?
The treatment of hyperthyroidism is described in detail in the Hyperthyroidismbrochure. Treatment includes antithyroid drugs (methimazole [Tapazole®]) or propylthiouracil [PTU]), radioiodine, and surgery. Although each treatment has its advantages and disadvantages, most patients will find one that is just right for them. Hyperthyroidism due to Graves' disease is, in general, easily controlled and safely treated, and treatment is almost always successful.

What will be the outcome of treatment?
No matter how your hyperthyroidism is controlled, you probably will have hypothyroidism someday. Hyperthyroidism tends to lead towards hypothyroidism, probably because of low-grade inflammation within your thyroid gland. Hypothyroidism will occur sooner if your thyroid has been damaged by radioactive iodine or removed in an operation. Even if you are treated with antithyroid drugs alone, hypothyroidism still can occur.

Because of this natural tendency to progress toward hypothyroidism sometime after you have been hyperthyroid, every patient who has ever had hyperthyroidism due to Graves' disease should have blood tests at least once a year to measure thyroid function. Low thyroid hormone levels cause your pituitary gland to produce increased amounts of thyroid-stimulating hormone (TSH). A high TSH blood level is the most sensitive indicator of hypothyroidism, and so your annual thyroid evaluation should always include a TSH test. When hypothyroidism occurs, a thyroid hormone tablet taken once a day can treat it simply and safely (see the Hypothyroidism brochure).

Other family members at risk
Because Graves' disease is an inherited condition, examinations of the members of your family may reveal other individuals with thyroid problems.

Thyroid Nodules

What is a thyroid nodule?
The term thyroid nodule refers to any abnormal growth of thyroid cells into a lump within the thyroid. Although the vast majority of thyroid nodules are benign (noncancerous), a small proportion of thyroid nodules do contain thyroid cancer. Because of this possibility, the evaluation of a thyroid nodule is aimed at discovering a potential thyroid cancer.


What are the symptoms of a thyroid nodule?
Most thyroid nodules do not cause any symptoms. Your doctor usually discovers them during a routine physical examination, or you might notice a lump in your neck while looking in a mirror. If the nodule is made up of thyroid cells that actively produce thyroid hormone without regard to the body's need, a patient may complain of hyperthyroid symptoms (see the Hyperthyroidism brochure). A few patients with thyroid nodules may complain of pain in the neck, jaw, or ear. If the nodule is large enough, it may cause difficulty swallowing or cause a "tickle in the throat" or shortness of breath if it is pressing on the windpipe. Rarely, hoarseness can be caused if the nodule irritates a nerve to the voice box.


What causes a thyroid nodule?
The thyroid nodule is the most common endocrine problem in the United States. The chances are 1 in 10 that you or someone you know will develop a thyroid nodule. Although thyroid cancer is the most important cause of the thyroid nodule, fortunately it occurs in less than 10% of nodules (see the Thyroid Cancer brochure). This means that about 9 of 10 nodules are benign (noncancerous). The most common types of noncancerous thyroid nodules are known as colloid nodules and follicular neoplasms. If a nodule produces thyroid hormone without regard to the body's need, it is called an autonomous nodule, and it can occasionally lead to hyperthyroidism. If the nodule is filled with fluid or blood, it is called a thyroid cyst.

We do not know what causes most noncancerous thyroid nodules to form. A patient with hypothyroidism may also have a thyroid nodule, particularly if the cause is the inflammation known as Hashimoto's thyroiditis (see Hypothyroidism brochure). Sometimes a lack of iodine in the diet can cause a thyroid gland to produce nodules. Some autonomous nodules have a genetic defect that causes them to grow.


How is the thyroid nodule diagnosed?
Since most patients with thyroid nodules do not have symptoms, most nodules are discovered during an examination of the neck for another reason, such as during a routine physical examination or when you are sick with a cold or flu. Once the nodule is discovered, your doctor will try to determine whether the lump is the only problem with your thyroid or whether the entire thyroid gland has been affected by a more general condition such as hyperthyroidism or hypothyroidism. Your physician will feel the thyroid to see whether the entire gland is enlarged, whether there is a single nodule present, or whether there are many lumps or nodules in your thyroid. The initial laboratory tests may include blood tests to measure the amount of thyroid hormone (thyroxine, or T4) and thyroid-stimulating hormone (TSH) in your blood to determine whether your thyroid is functioning normally. Most patients with thyroid nodules will also have normal thyroid function tests.

Rarely is it possible to determine whether a thyroid nodule is cancerous by physical examination and blood tests alone, and so the evaluation of the thyroid nodule often includes specialized tests such as a thyroid fine needle biopsy, a thyroid scan, and/or a thyroid ultrasound.

Thyroid fine needle biopsy
A fine needle biopsy of a thyroid nodule may sound frightening, but the needle used is very small and a local anesthetic can be used. This simple procedure is done in the doctor's office. It does not require any special preparation (no fasting), and patients usually return home or to work after the biopsy without any ill effects. For a fine needle biopsy, your doctor will use a very thin needle to withdraw cells from the thyroid nodule. Ordinarily, several samples will be taken from different parts of the nodule to give your doctor the best chance of finding cancerous cells if a tumor is present. The cells are then examined under a microscope by a pathologist.

The report of a thyroid fine needle biopsy will usually indicate one of the following findings:

  1. The nodule is benign (noncancerous). This result is obtained in 50% to 60% of biopsies and often indicates a colloid nodule. The risk of overlooking a cancer when the biopsy is benign is generally under 3 in 100 and is even lower when the biopsy isreviewed by an experienced pathologist at a major medical center. Generally, these nodules need not be removed, but another biopsy may be required in the future, especially if they get bigger.

  2. The nodule is malignant (cancerous). This result is obtained in about 5% of biopsies and often indicates papillary cancer, one of the most common thyroid cancers. All of these nodules should be removed surgically, preferably by an experienced thyroid surgeon.

  3. The nodule is suspicious. This result is obtained in about 10% of biopsies and indicates either a follicular adenoma (noncancerous) or a follicular cancer. Often, your doctor may want to obtain a thyroid scan to determine which nodules should be removed surgically.

  4. The biopsy is nondiagnostic or inadequate. This result is obtained in up to 20% of biopsies and indicates that not enough cells were obtained to make a diagnosis. This is a common result if the nodule is a cyst. These nodules may be removed surgically or be re-evaluated with second fine needle biopsy, depending on the clinical judgment of your doctor.

Thyroid scan
The thyroid scan uses a small amount of a radioactive substance, usually radioactive iodine, to obtain a picture of the thyroid gland. Because thyroid cancer cells do not take up radioactive iodine as easily as normal thyroid cells do, this test is used to determine the likelihood that a thyroid nodule contains a cancer. If done as the first test, the thyroid scan is used to determine those patients who most need a biopsy. The scan usually gives the following results.

  1. The nodule is cold. In other words, the nodule is not taking up radioactive iodine normally. This patient is referred for a fine needle biopsy of the nodule.

  2. The nodule is functioning. Its uptake of radioactive iodine is similar to that of normal cells. A biopsy is not needed right away since the likelihood of cancer is very low.

  3. The nodule is hot. Its uptake of radioactive iodine is greater than that of normal cells. The likelihood of cancer is extremely rare, and so biopsy is usually not necessary.

If the fine needle biopsy was done as the first test, then a scan is usually ordered to evaluate a suspicious biopsy result. In this case, patients with a "cold" nodule result should have their nodule removed. Patients with "functioning" or "hot" nodules on a scan and a suspicious biopsy can be watched, and surgery is not immediately necessary.

Thyroid ultrasound
The thyroid ultrasound uses high-frequency sound waves to obtain a picture of the thyroid. This very sensitive test can easily determine if a nodule is solid or cystic, and it can determine the precise size of the nodule. The thyroid ultrasound can be used to keep an eye on thyroid nodules that are not removed by surgery to determine if they are growing or shrinking. Some ultrasound characteristics of a nodule are more frequent in thyroid cancer than in noncancerous nodules. Even so, the thyroid ultrasound alone is rarely able to determine if a nodule is a thyroid cancer. The thyroid ultrasound also can be used to assist the placement of the needle within the nodule during a fine needle biopsy, especially if the nodule is hard to feel. Finally, the thyroid ultrasound can identify nodules that are very small and cannot be felt during a physical examination. The clinical importance of these very small nodules is uncertain; however, the ultrasound provides a means by which an accurate fine needle biopsy can be performed if your doctor thinks a biopsy is needed.


How are thyroid nodules treated?
All thyroid nodules that are found to contain a thyroid cancer, or that are highly suspicious of containing a cancer, should be removed surgically by an experienced thyroid surgeon. Most thyroid cancers are curable and rarely cause life-threatening problems (see Thyroid Cancer brochure ). Any thyroid nodule not removed needs to be watched closely, with an examination of the nodule every 6 to 12 months. This follow-up may involve a physical examination by a doctor or a thyroid ultrasound or both. Occasionally, your doctor may want to try to shrink your nodule by treating you with thyroid hormone (see Thyroid Hormone Treatment brochure) at doses slightly higher that your body needs (called suppression therapy). Whether you are on thyroid hormone suppression therapy or not, a repeat fine needle biopsy may be indicated if the nodule gets bigger. Also, even if the biopsy is benign, surgery may be recommended for removal of a nodule that is getting bigger.


Cancer of the Thyroid

Thyroid cancer is the most common endocrine-related cancer; however, it is rare compared to other cancers. In the United States there are only about 20,000 new patients annually. Even though the diagnosis of cancer is terrifying, the outlook for patients with thyroid cancer is usually excellent. First, most thyroid cancer is easily curable with surgery. Second, thyroid cancer rarely causes pain or disability. Third, effective and well-tolerated treatment is available for the most common forms of thyroid cancer.


What are the symptoms of thyroid cancer?
The key sign of thyroid cancer is a lump (nodule) in the thyroid, and most thyroid cancers do not cause any symptoms (see Thyroid Nodule brochure). Instead, your doctor may discover the nodule during a routine physical examination or you may notice a lump in your neck while looking in a mirror. A few patients with thyroid cancer complain of pain in the neck, jaw or ear. If the cancer is large enough, it may cause difficulty swallowing or cause a "tickle in the throat" or shortness of breath if it is pressing on the windpipe. Rarely, hoarseness can be caused if the cancer irritates a nerve to the voice box.


What causes thyroid cancer?
Thyroid cancer is more common in people who have a history of exposure of the thyroid gland to radiation, have a family history of thyroid cancer, and are older than 40 years of age. However, for most patients, we do not know the specific reason why they develop thyroid cancer.

Exposure of the thyroid to radiation causes thyroid cancer in susceptible patients, especially if the exposure occurred as a child. Many years ago (ie, in the 1940s and 1950s), radiation exposure included X-ray treatments for acne, inflamed tonsils, adenoids, lymph nodes, or an enlarged thymus gland. X-rays also were used to measure foot sizes in shoe stores. Currently, X-ray exposure is usually limited to treatment of serious cancers such as Hodgkin's disease (cancer of the lymph nodes). Routine X-ray exposure (eg, dental X-rays, chest X-rays, mammograms) does not cause thyroid cancer.

Thyroid cancer can be caused by absorbing radioactive iodine released during a nuclear power plant emergency, such as the 1986 nuclear accident at the Chernobyl power plant in Russia. Children who were exposed were the most affected, and cancers were seen within a few years of that disaster. You can be protected from developing thyroid cancer due to a nuclear power plant emergency by taking potassium iodide, which blocks your thyroid from absorbing radioactive iodine. The United States government is currently developing guidelines to distribute potassium iodide to people living near nuclear power plants.


How is thyroid cancer diagnosed?
A diagnosis of thyroid cancer is made on the basis of a biopsy of a thyroid nodule or after the nodule is removed during surgery (see Thyroid Nodule brochure). Although thyroid nodules are very common, less than 1 in 10 harbor a thyroid cancer.

What are the types of thyroid cancer?

Papillary thyroid cancer.Papillary thyroid cancer is the most common type, making up about 70% to 80% of all thyroid cancers. Papillary thyroid cancer can occur at any age. There are only about 12,000 new cases of papillary cancer in the United States each year, but because these patients have such a long life expectancy, we estimate that 1 in a 1000 people in the United States have or have had this form of cancer. Papillary cancer tends to grow slowly and to spread first to lymph glands in the neck. Unlike some other tumors, the generally excellent outlook for papillary cancer is usually not affected by spread of the cancer to the lymph nodes.

Follicular thyroid cancer. Follicular thyroid cancer, which makes up about 10% to 15% of all thyroid cancers in the United States, tends to occur in somewhat older patients than does papillary cancer. As with papillary cancer, follicular cancer first can grow into lymph nodes in the neck. Follicular cancer is also more likely than papillary cancer to grow into blood vessels and from there to spread to distant areas, particularly the lungs and bones.

Medullary thyroid cancer.Medullary thyroid cancer, which accounts for 5% to 10% of all thyroid cancers, is more likely to run in families and be associated with other endocrine problems. In fact, medullary thyroid cancer is the only thyroid cancer that can be diagnosed by genetic testing of the blood cells. In family members of an affected person, a positive test for the RET proto-oncogene can lead to an early diagnosis of medullary thyroid cancer and, subsequently, curative surgery to remove it.

Anaplastic thyroid cancer.Anaplastic thyroid cancer is the most advanced and aggressive thyroid cancer and is the least likely to respond to treatment. Fortunately, anaplastic thyroid cancer is rare and found in less than 5% of patients with thyroid cancer.


What is the treatment for thyroid cancer?

Surgery. The primary therapy for all forms of thyroid cancer is surgery. The generally accepted approach is to remove the entire thyroid gland, or as much of it as can be safely removed. After surgery, patients need to be on thyroid hormone for the rest of their life (see Thyroid Hormone Treatment brochure). Often the thyroid cancer is cured by surgery alone, especially if the cancer is small. If the cancer is large within the thyroid or if it has spread to lymph nodes or if your doctor feels that you are at high risk for recurrent cancer, radioactive iodine can be used as a "magic bullet" to destroy thyroid cancer cells after removal of the thyroid gland by surgery.

Radioactive iodine therapy. A major reason for the usually excellent prognosis for patients with papillary and follicular thyroid cancer is that radioactive iodine can be used as a magic bullet to seek out and destroy thyroid cancer cells with little or no damage to other tissues in the body. Thyroid cells normally concentrate iodine from the bloodstream to use to produce the thyroid hormones. By contrast, thyroid cancer cells usually take up only tiny amounts of iodine. However, high levels of thyroid stimulating hormone (TSH) can arouse thyroid cancer cells to take up significant amounts of iodine.

If your doctor recommends radioactive iodine therapy, high levels of TSH will be produced in your body by making you hypothyroid for a short time-either by not starting thyroid hormone pills after the thyroid gland is removed or by stopping your thyroid hormone pills if you are already on medication. Sometimes, to minimize your symptoms of hypothyroidism, your doctor may prescribe Cytomel™ (T3) to take while you are becoming hypothyroid. Also, you may be asked to go on a low iodine diet before the treatment to increase the effectiveness of the radioactive iodine. Once the TSH level is high enough, a whole body iodine scan is done by administering a small dose of radioactive iodine to determine if there are remaining thyroid cells that need to be destroyed. If enough cells show up on the whole-body iodine scan, a large dose of radioactive iodine (I131) is given, and then the thyroid pills are re-started. Radioactive iodine therapy has proved to be safe and well-tolerated, and it has even been able to cure cases of thyroid cancer that had already spread to the lungs.

What is the follow-up for patients with thyroid cancer?
Periodic follow-up examinations are essential for all patients with thyroid cancer because the thyroid cancer can return-sometimes many years after the apparently successful initial treatment. These follow-up visits include a careful history and physical examination, with particular attention to the neck area, as well as blood tests to determine if any changes of your thyroid hormone dose are needed. In particular, blood tests are done to measure the levels of T4 and TSH as well as a thyroid cell protein, thyroglobulin, which serves as a thyroid cancer marker. The thyroid hormone dose is adjusted to lower the TSH level into the low range. If the thyroglobulin level is still detectable despite a TSH in the low range, it means that there still are potential thyroid cancer cells functioning in the body. This finding may lead to additional tests and possible further treatment with radioactive iodine and/or surgery. Unfortunately, in some thyroid cancer patients the presence of interfering antibodies in the blood may prevent accurate thyroglobulin measurement.

In addition to routine blood tests, your doctor may want to repeat periodically a whole-body iodine scan to determine if any thyroid cells remain. This can be done after your TSH level is raised, either by stopping your thyroid hormone and your becoming hypothyroid (see above) or by administering Thyrogen™ (synthetic human TSH) injections.

What is the prognosis of thyroid cancer?
Overall, the prognosis of thyroid cancer is very good. In general, the prognosis is better in younger patients than in those over 40 years of age. Patients with papillary carcinoma who have a primary tumor that is confined to the thyroid gland itself have an excellent outlook: only 1 out of every 100 such patients have died of thyroid cancer by 25 years later. The prognosis is not quite as good in patients over the age of 40, or in patients with tumors larger than 4 centimeters (1½ inches) in diameter. Still, even those patients who are unable to be cured of their thyroid cancer are able to live a long time and feel well despite their cancer.


Nuclear Radiation and the Thyroid


Why does the thyroid gland need special protection after a release of radioactive material?
The thyroid gland needs iodine to produce the hormones that regulate the body's energy and metabolism. The thyroid absorbs available iodine from the bloodstream. The gland cannot distinguish between stable (regular) iodine and radioactive iodine, and will absorb whatever it can. In babies and children, the thyroid gland is one of the most radiationsensitive parts of the body. Most nuclear explosions release radioactive iodine. When thyroid cells absorb too much radioactive iodine, it can cause thyroid cancer. Babies and young children are at highest risk. The risk is much lower for people over age 40. Thyroid cancer seems to be the only cancer whose incidence rises after a radioactive iodine release. KI protects only the thyroid, but it is the organ that most needs protecting.

What is KI?
Potassium iodide (KI) is the same form of iodine used to iodize table salt. KI floods the thyroid with iodine, thus preventing radioactive iodine from being absorbed. If taken at the proper time, KI protects the thyroid from radioactive iodine from all sources - air, food, milk, and water. KI is a nonprescription drug that can be bought over the internet and at some pharmacies. KI is made in pill and liquid forms. The two FDA-approved brands of full adult dose 130-mg KI pills are IOSAT® (Anbex, Inc.) and Thyro-Block® (Medpointe, Inc.). The FDA-approved brand of 65-mg KI pills is ThyroSafe® (Recip US). Properly packaged, KI's shelf life is at least 5 years and possibly as long as 11 years. If you accidentally take a very old pill, it may not work fully but it won't hurt you.

What is the proof that KI works?
After the 1986 Chornobyl (formerly called "Chernobyl") nuclear accident, shifting winds blew a radioactive cloud all over Europe. As many as 3,000 people exposed to that radiation have already developed thyroid cancer. Most victims had been babies or young children living in Ukraine, Belarus, or Russia at the time of the accident. According to a UN report released in February 2002, another 8,000 to 10,000 exposed people may develop thyroid cancer within the next 10 years. Poland, immediately adjacent to Belarus and Ukraine, distributed KI to its people and does not appear to have had an increase in thyroid cancer.

When should KI be taken?
Taken 6-12 hours before exposure to radioactive iodine, KI fills the thyroid cells and prevents the gland from absorbing radioactive iodine. KI is also protective if taken within the first few hours after exposure to radioactive iodine. People should take one dose a day, only while they are being exposed to radioactive iodine and one day afterward. KI should be used only under instruction from local health authorities. Not every radioactive release includes the radioactive iodine that can cause thyroid cancer. For example, a "dirty bomb" is not likely to contain radioactive iodine because it has a short half-life. (A "dirty bomb" is a conventional bomb mixed with radioactive material, and designed to explode spewing out the radioactive isotopes and contaminating a wide area.) Only health authorities can determine which radioactive isotopes are released during a nuclear event, and, if radioactive iodine is released, when to take KI and how long to keep taking it.

What are the recommended KI doses?
The U.S. Food and Drug Administration (FDA) has published general recommendations for minimum KI doses: a full 130-mg pill for adults, 65 mg for children 3 to 18 years old, 32 mg for babies 1 month to 3 years old, and 16 mg for newborns up to 1 month old. In the U.S., KI pills are now sold in both 130-mg and 65-mg doses. The pills are scored to make it easier to cut them up for children's doses. An April 2002 FDA statement says that "absolute precision in dosing is generally not critical to safety or efficacy" and "the overall benefits of KI far exceed the risks of overdosing, especially in children." According to the FDA, children over 1 month old can safely be given a full-dose 130-mg pill on each of 2 consecutive days. However, newborns should be given only a 16-mg dose. The easiest way to prepare a 16-mg dose is to dissolve a 130-mg pill in 8 oz of a clear liquid and feed the newborn 1 oz of the liquid. Another alternative is to give the newborn 16 mg of the liquid form of KI (saturated solution of potassium iodide [SSKI]), which requires a doctor's prescription. For FDA suggestions on preparing KI doses for children, see http://www.fda.gov.

Who should not take KI?
Millions of people have taken KI but few serious side-effects have been reported. The only people who should not take KI are those who have had a major allergic reaction to iodine. In the amounts that the FDA recommends, and for the few days that public health officials expect people to need KI, patients with thyroid disease can safely take the pills in the regularly recommended doses. During a nuclear emergency, KI's benefit far outweighs any potential risk. Adults over age 40 do not need KI at all unless they are exposed to extremely high levels of radioactive iodine.

If taken for long enough, KI can cause temporary hypothyroidism (underactive thyroid gland). "Long enough" is different for every person. Prolonged treatment can become a serious problem for very young children. Such children should be seen afterward by a health professional. Patients with Graves' hyperthyroidism or with autonomous functioning thyroid nodules should also be seen.

Why worry so much about thyroid cancer if most people survive it?
In general, 90% of patients survive thyroid cancer. The post-Chornobyl cancers have been aggressive and have been unusual in affecting children younger than 10 years of age. Thyroid cancer survivors always remain at risk for recurrence and require lifelong medical care. Likewise, the people who were exposed to radioactive iodine from the Chornobyl accident but have not developed thyroid cancer remain at risk for life and must continue to be tested. The demands of regular testing and care for this large population are putting a heavy burden on both patients and health care systems.

How should KI be incorporated into an overall emergency plan?
KI is an adjunct to evacuation, sheltering (staying in an unventilated room with the doors and windows closed), and avoiding contaminated food, milk, and water. KI should not take the place of any other protective measure.

Won't having KI pills lull people into a false sense of security?
Not likely. Local authorities recommend that people leave the vicinity of a nuclear emergency as quickly as possible. People are being taught that KI is just a supplement to evacuation.

Why waste time taking a pill if you're being told to evacuate?
Because nuclear releases are unpredictable but traffic jams are likely to delay speedy evacuation, people should take their KI before they evacuate, following instructions from local health officials.

Why offer KI to people just within 10 or 20 miles of a plant?

Can't radiation be harmful farther away?
KI distribution should not be limited to 10 or 20 miles. No one can predict how far a radioactive iodine cloud might spread. After Chornobyl, higher than expected rates of thyroid cancer were found more than 200 miles away from the nuclear plant. Thus, no one can predict how far from a nuclear plant the U.S. should distribute KI if it is to protect every person who might be exposed to radioactive iodine. Because there is no right answer, the American Thyroid Association recommends three levels of coverage, determined by distance from the nuclear plant (see table below). Ring Distance from nuclear plant Action 1 0-50 miles Distribute KI in advance ("predistribute") to individual households, with extra stockpiles stored at emergency reception centers 2 50-200 miles Stockpile KI in local public facilities such as schools, hospitals, clinics, post offices, and police and fire stations, for distribution upon notification by local health officials 3 >200 miles Make KI available from the Department of Health and Human Services' National Pharmaceutical Stockpile

What do U.S. government agencies recommend?
KI is endorsed for radiation protection by the U.S. Food and Drug Administration. The Department of Health and Human Services has included KI in the National Pharmaceutical Stockpile for use in health emergencies. In December 2001, the Nuclear Regulatory Commission wrote to the 34 states that either have a functioning nuclear power plant or are within 10 miles of another state's plant; the letter offered two free KI pills for each resident within the 10-mile "emergency zone" surrounding active plants, and an extra supply to be provided for transients. As of September 13, 2002, Alabama, Arizona, California, Connecticut, Delaware, Florida, Maryland, Massachusetts, New Hampshire, New Jersey, New York, North Carolina, Ohio, Pennsylvania, Vermont and Virginia had taken up the NRC on its offer. Instead of accepting the NRC offer, Illinois chose to distribute KI pills provided by the operator of most of the state's nuclear plants. Tennessee has had its own KI program in place since 1981. Maine has discontinued its state program.

The Public Health Security and Bioterrorism Preparedness and Response Act of 2002, enacted by Congress in May 2002, creates a mechanism to extend the radius of KI distribution to communities within 20 miles of nuclear plants, and directs the President to decide which agency or agencies will oversee KI stockpiling and distribution. Distribution under the new law could begin as early as June 2003.

Won't distribution and public education be expensive and time-consuming?
Possibly, although the potential benefit of KI far outweighs the cost. The Bioterrorism Act directs the National Academy of Sciences to study "the most effective and safe way to distribute and administer potassium iodide tablets on a mass scale." The National Academy of Sciences panel should address many of the decisions still to be made, for example: Who should be responsible for distribution? Within 50 miles of a nuclear plant, how should pills best be predistributed to families to store at home, before the time of need? Within 50 miles of a plant, should pills also be kept at local schools, clinics, post offices, and police and fire stations for distribution during an emergency? How should children be treated at school? How should stockpiles be maintained? Provision must also be made to educate the public about why KI is important, what it can and cannot do, and how and when to use it. The states that want KI are working out individual distribution and education plans, as part of their overall emergency plans. Vermont's draft plan is posted on its web site (http://healthvermont.gov.) It is noteworthy that the offer of KI has led some states to reassess their overall emergency response plans.

What are other countries doing?
The World Health Organization endorses KI. France, Ireland, Sweden, and Switzerland not only stockpile KI but predistribute it to their populations.

What does the American Thyroid Association recommend?
The American Thyroid Association (ATA) has been urging KI stockpiling since 1984. ATA members have been studying the Chornobyl nuclear accident and caring for its victims. The Association's recommendations are outlined in the public health statement American Thyroid Association endorses potassium iodide for radiation emergencies. This plan is endorsed by the American Association of Clinical Endocrinologists, the Lawson Wilkins Pediatric Endocrine Society, and the Thyroid Foundation of America.

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