What Is It?
A thyroid disorder is an autoimmune condition related to the thyroid gland, a small gland that manufactures and stores thyroid hormones. A thyroid disorder impacts the metabolic processes and may be characterized by nervousness or tiredness, weight changes, weak muscles, impaired memory and irregular menstrual flow.
Your thyroid is one of your body's most important glands. When your thyroid doesn't work properly, it can cause you to feel nervous or tired; make your muscles weak; cause weight gain or loss; impair your memory; and affect your menstrual flow. A thyroid disorder can also cause miscarriage and infertility.
About 20 million Americans—more of them women than men—are affected by a thyroid disease or disorder, according to the American Thyroid Association (ATA). In fact, an estimated one in eight women will develop a thyroid disorder at some time in her life.
Thyroid Disease in Women
Women are five to eight times more likely to have thyroid dysfunction than men, but most don't know they have it. Women often overlook their symptoms or mistake them for symptoms of other conditions. For example, women are at particularly high risk for developing thyroid disorders following childbirth. Symptoms such as fatigue and depression are common during this period, but these are also symptoms of thyroid disease. The ATA estimates that more than half of thyroid conditions remain undiagnosed.
How the Thyroid Works
The thyroid is a butterfly-shaped gland you can feel at the base of your neck, just below your larynx (voice box). Two lobes (the "wings" of the butterfly) fit on either side of your windpipe.
The thyroid gland manufactures and stores thyroid hormone (TH), often referred to as the body's metabolic hormone. Among other actions, TH stimulates enzymes that combine oxygen and glucose, a process that increases your basal metabolic rate (BMR) and body heat production. The hormone also helps maintain blood pressure, regulates tissue growth and development and is critical for skeletal and nervous system development. It plays an important role in the development of the reproductive system.
Types of Thyroid Disorders
The thyroid gland can malfunction in one of three ways:
Hypothyroidism
When too little TH is released, the body's metabolic rate decreases, and the body slows down. Hypothyroidism often goes undiagnosed because its symptoms are often mistaken for or attributed to other conditions. Symptoms include:
Hypothyroidism can occur spontaneously, develop during or after pregnancy or after treatment for hyperthyroidism. You can be born with it or it can be caused by Hashimoto's thyroiditis, the leading cause of hypothyroidism in the United States.
Named for the Japanese health care professional who first described it in detail, Hashimoto's thyroiditis is an autoimmune disease. That means the immune system attacks the body's healthy tissues instead of fighting off invading bacteria or viruses. In this case, the immune system produces antibodies to attack the thyroid gland as if it were a foreign substance that needed to be destroyed. The resulting damage leads to reduced production of TH.
Hyperthyroidism
When too much TH is released, the body's metabolic rate increases, and your metabolism speeds up. Symptoms of hyperthyroidism include:
Hyperthyroidism can be caused by nodules composed of thyroid cells that produce TH without regard to the body's need. It can also develop during or after pregnancy and may be caused by Graves' disease. Symptoms of hyperthyroidism may also result from overtreatment of hypothyroidism with synthetic TH or from thyroiditis, an inflammation of the thyroid gland, which leads to an overproduction of TH.
Graves' disease, another autoimmune condition, is the leading cause of hyperthyroidism, accounting for 85 percent of hyperthyroidism cases. Graves' disease differs from Hashimoto's thyroiditis in that the antibodies turn the thyroid on, causing the thyroid gland to enlarge and overproduce TH. Other antibodies may also attack eye muscle tissue and the skin on the front of the lower leg. Graves' disease was named for Robert Graves, an Irish health care professional who first discussed this form of hyperthyroidism. It is a completely treatable disease and is rarely fatal.
Thyroid nodules
Thyroid nodules are the most common thyroid disorder, occurring in up to 50 percent of people over the age of 50. Many of these nodules are small (less than 1 centimeter) but some can reach more than 5 centimeters with few, if any, symptoms. Indeed, many nodules are only discovered when people have imaging studies of their necks, such as a chest CT scan or a carotid ultrasound. An estimated one in 10 Americans will develop a significant thyroid nodule at some point in their lives. Ranging from as small as a millimeter to as large as several inches, thyroid nodules themselves don't represent illness. Nodules do, however, indicate an underlying problem with the thyroid and should be evaluated if they are discovered.
The majority of nodules are benign discrete clumps of thyroid cells, which don't function like normal thyroid tissue. Other nodules turn out to be simple cysts. However, there is a slight chance that a thyroid nodule is cancerous—less than 10 percent of nodules are cancerous—so it is important to have a health care professional assess all growths.
While most nodules have no symptoms, are never detected and are harmless, some can be large enough to press against the windpipe and cause difficulty swallowing or a cough. A nodule can also become overactive, suppressing the rest of the gland and causing hyperthyroidism.
Thyroid hormone (TH), which is stored and produced by the thyroid gland, actually consists of two hormones: thyroxine, known as T4, and tri-iodothyronine, known as T3. The production of T4 and T3 is controlled by thyroid stimulating hormone (TSH). The pituitary gland produces TSH, controlling the production of TH by the thyroid gland. The pituitary gland acts like a sensor on a thermostat; if it senses too little TH in your blood, it releases TSH to tell your thyroid to produce more. Likewise, if your pituitary senses too much TH in the blood, it decreases production of TSH.
The best way to determine if your body is making too much or too little TH is by measuring blood levels of TSH. If the TSH level is abnormal, your health care professional may also want to test your blood for T3 and T4 levels. These blood tests provide an accurate picture of how the thyroid is functioning.
Hypothyroidism is diagnosed if TH levels are low to normal and TSH levels are high. To rule out Hashimoto's thyroiditis as the cause, your health care professional may check your blood for antithyroid antibodies.
Hyperthyroidism is suspected if TH levels are high and TSH levels are low. To determine if Graves' disease is the cause, your health care professional can check your blood for thyroid stimulating antibodies or give you a radioactive iodine uptake test.
Iodine is essential for the production of TH, so the thyroid absorbs it from the blood. During a radioactive iodine uptake test, you swallow a small amount of I-123 radioactive iodine. This form of radioactive iodine does not damage the thyroid. The thyroid absorbs and metabolizes this radioactive iodine within 24 hours. Special equipment is then used to measure the amount of radioactivity in the thyroid gland, and you usually have to return within six and 24 hours to have the radioactivity measured (although some labs only measure after 24 hours). If you have Graves' disease, the amount of radioactivity in the thyroid is high. If you have other forms of hyperthyroidism, such as an inflammation of the thyroid known as a thyroiditis, the radioactivity taken up by the thyroid will be low.
Thyroid Nodules
There are four ways to diagnose a thyroid nodule:
All nodules should be evaluated by a specialist, such as an endocrinologist or an internal medicine specialist, to determine if the nodule is caused by a thyroid cancer. In addition to ordering blood tests described earlier, your doctor will examine the structure of the thyroid gland using one or more of the following tests:
The treatment you receive depends on the type of thyroid disorder you have, what's causing it and your overall medical condition. In general, there are three categories of treatment: prescription medication, radioactive iodine and surgery (thyroidectomy).
Hypothyroidism
Hypothyroidism, including Hashimoto's thyroiditis, is the simplest of the three types of thyroid disorders to treat. It requires a daily dose of prescription synthetic T4, called levothyroxine sodium (L-thyroxine, L-T4). You and your health care professional will work together to find the right dose for you based on your symptoms and blood tests.
You'll need to take T4 for the rest of your life, although the dose may change. You will also need periodic blood tests to evaluate the dose.
Many years ago, the only treatment available for hypothyroidism was desiccated thyroid, the dried and powdered thyroid glands of animals. It contains both T4 and T3. While desiccated thyroid is still available today, few health care professionals advocate this "natural" therapy. Desiccated thyroid produces variable blood levels of thyroid hormones, not the steady and predictable levels needed for optimal health.
If your T4 dose is too low—if you remain somewhat hypothyroid—you may experience symptoms of hypothyroidism (depression, low body temperature, dry or itchy skin, poor memory, muscle aches, slowed reflexes, among other symptoms). If your dose is too high—if you become somewhat hyperthyroid—you may notice symptoms of hyperthyroidism (nervousness, weight loss, fast or irregular heart rate, changes in appetite, insomnia, muscle weakness or fatigue, decreased menstrual flow, among other symptoms). Over time, TH excess can increase your risk of an abnormal heart rhythm or osteoporosis.
In the United States, levothyroxine is available as four branded products (Levoxyl, Levothroid, Synthroid and Unithroid) and several generic versions. All of the branded and generic preparations contain the same hormone—levothyroxine—and are effective in treating hypothyrodism. However, because the preparations may differ in the amount of levothyroxine they contain, many experts have expressed concerns about potential adverse effects caused by switching between manufacturers as will happen with the generic T4 preparations. For example, the 100 mcg dose of one preparation may contain the same amount of T4 as the 112 mcg dose of another preparation, so switching between preparations may actually represent a dose change.
Generally, you should stick with one T4 product for treating hypothyroidism, generally a branded T4. However, because of insurance issues, you may not have a choice between branded or generic. If possible, stick to one generic manufacturer to keep the level fairly consistent in your body. If you must change generics or brands, talk to your health care professional—he or she may have to repeat your blood tests and change the dose to maintain the desired effect or prevent toxicity.
If you do switch brands or change to a generic T4, you should have your TSH level checked six weeks later. In general, because multiple manufacturers produce generic versions, those on generic T4 should have their TSH levels monitored more frequently.
Hyperthyroidism
If you are diagnosed with hyperthyroidism, including Graves' disease, your health care professional will consider several factors to determine the best treatment for you. These include your age, your general health and the cause and severity of the hyperthyroidism. Available treatments include I-131 radioactive iodine (the form of radioactive iodine that damages thyroid tissue), antithyroid drugs and surgery.
A dose of radioactive iodine works to damage the thyroid gland, ending the hyperthyroidism. After the iodine is administered, the gland shrinks and blood levels of TH drop. In most, the hyperthyroidism is completely resolved within three to six months. The main side effect is the development of hypothyroidism. Occasionally, you may develop a sore throat one or two weeks after the treatment.
Some people with hyperthyroidism receive antithyroid drugs such as propylthiouracil (PTU) or methimazole (Tapazole). These drugs are designed to interfere both with the thyroid gland's uptake of iodine and with one or more of the steps required for the thyroid to make TH. Because iodine is essential for TH production, reducing the amount of iodine the thyroid gets reduces the amount of TH it produces. Some people with Graves' disease may go into a long-term remission of more than a year after one or two years of treatment, after which the drugs are stopped.
Surgery to remove part of the overactive thyroid gland is occasionally recommended to treat hyperthyroidism. Like radioactive iodine, people who undergo surgery usually become hypothyroid. Complications include damage to the parathyroid glands that control the body's calcium levels and damage to the nerves that control your vocal cords, leading to hoarseness.
Since any of the three treatments for hyperthyroidism can lead to hypothyroidism, it's important that you learn to recognize the symptoms of too little thyroid hormone: depression, low body temperature, dry or itchy skin, poor memory, muscle aches and slowed reflexes. Let your health care professional know if you experience any symptoms.
Nodules
If a nodule is benign—as most are—it will probably simply need to be monitored, not treated. If a biopsy is unclear or identifies a malignancy, then you will need a thyroidectomy, or removal of all or part of the thyroid.
A thyroidectomy is performed under general anesthesia and takes about two hours. If the biopsy showed a malignancy, the surgeon usually removes the entire thyroid and some surrounding lymph nodes. If the biopsy was unclear, the surgeon may remove just one lobe of the thyroid and, while you're still under the anesthetic, wait for it to be tested for cancerous cells. If these cells are present, the surgeon removes the other lobe. If the cancer has spread outside the thyroid, the surgeon may also remove the lymph nodes in your neck.
If you have thyroid cancer you may require treatment with a large dose of the I-131 form of radioactive iodine about six weeks after surgery to destroy any remaining cancerous tissue. The use of radioactive iodine in thyroid cancer has changed in recent years and is beign used less frequently. This is because many patients with small cancers, who are at low risk for cancer recurrence, do not appear to benefit from radioactive iodine since they are most likely cured with surgery alone. You should discuss this with a thyroid cancer specialist. You also begin lifelong TH replacement therapy. In most cases, the surgery and radioactive iodine cure the cancer.
As with other surgery, the minor risks include infection, bleeding and scar tissue on the neck. Major side effects from surgery are rare and involve complications to neck structures close to the thyroid, including damage to the parathyroid glands that control your body's calcium levels and damage to the nerves that control your vocal cords, leading to hoarseness. These complications, however, occur in less than 1 percent of patients operated on by experienced surgeons. If the parathyroid glands are damaged during surgery, you'll need calcium supplements and possibly other drugs.
There is no way to prevent thyroid disorders, but by managing the disorder you can prevent complications. For instance, left untreated, Graves' disease can weaken your heart muscles, leading to heart failure, and can lead to osteoporosis or severe emotional disorders. Depression, a symptom of hypothyroidism, can also have devastating effects if you don't treat the underlying condition.
Thus, even if your treatment is working, keep the following in mind:
If you begin thyroid hormone replacement therapy:
Review the following Questions to Ask about thyroid disorders so you're prepared to discuss this important health issue with your health care professional.
Thyroiditis is an inflammation of the thyroid gland. It can result in a nodule, or it can cause hypothyroidism, hyperthyroidism or both (one followed by the other).
The thyroid gland makes, stores and releases thyroid hormone (TH), which is known as the body's metabolic hormone. TH tells the body how fast to use energy. If there is too much TH in your blood, you become hyperthyroid, and you use energy too fast. If there is too little TH in your blood, you become hypothyroid, and you use energy too slowly.
The most common cause of hypothyroidism in the United States is an autoimmune disease known as Hashimoto's thyroiditis. Hypothyroidism also can occur spontaneously; can develop during or after pregnancy; can be present at birth; or can develop after hyperthyroid treatment.
Graves' disease is not curable, but it is rarely fatal and is a completely treatable disease. Remission may be permanent, but the thyroid should be checked periodically to be sure. Severe stress can aggravate a recurrence.
Pregnant women are at an increased risk of developing thyroid dysfunction as compared to the general population. Any woman with a prior history of a thyroid problem, a family history of thyroid disease or symptoms of thyroid dysfunction should be tested for thyroid dysfunction as soon as she knows she is pregnant. TH (T4) is absolutely safe to take during pregnancy and is essential for the health of the fetus if you are diagnosed with hypothyroidism. If you are diagnosed with hyperthyroidism, antithyroid drugs may be used. If a woman is allergic to these drugs, surgery may also be considered at certain times during the pregnancy (the second trimester). Radioactive iodine is not an option during pregnancy because it will pass into the fetus and damage its thyroid gland.
Untreated hyperthyroidism or overtreated hypothyroidism can increase your risk for osteoporosis. However, thyroid hormone treatment for hypothyroidism that keeps the thyroid levels in the normal range does not increase the risk of osteoporosis. Bones generally renew themselves in a process called bone turnover or resorption. Because hyperthyroidism increases the body's metabolism, bone turnover also is increased. This increase causes old bone tissue to dissolve before new tissue is fully formed, which does not give the body enough time to produce enough minerals for the new bones. The result: thin or weakened bones—osteoporosis.
The use of thyroid hormone or antithyroid drug treatment can, over time, produce the opposite effect, especially if the dose of medication given is too high. This means that if you are taking antithyroid medication for hyperthyroidism, you could become hypothyroid; if you are taking thyroid hormone medication for hypothyroidism, you could become hyperthyroid. Pay close attention to how you feel and be aware of the symptoms for each type of thyroid disorder.
X-rays used today to take images of the head and chest are not harmful. While the thyroid does get exposed to tiny doses of radiation during dental X-rays, there is no evidence to date that these low doses cause thyroid cancer. However, it is prudent (and mostly standard practice) to use a thyroid shield when getting dental X-rays.
In contrast to X-rays performed today, radiation procedures from the 1920s to the 1960s for inflamed tonsils, adenoids, lymph nodes or an enlarged thymus gland could put you at risk. There is a clearly established relationship between thyroid cancer and these early radiation treatments of the head and neck. If you believe you were exposed to this type of treatment as a child or an adult, you should have your thyroid checked annually.
There is no evidence that the tiny amounts of radiation from mammograms even reach the thyroid and, thus, there is no evidence that mammograms increase your risk for thyroid cancer. It is not necessary to use a thyroid shield during a mammogram.
No. Some people have normally high or low waking body temperatures. The only way to accurately diagnose a thyroid disorder is with a highly sensitive TSH blood test.
For information and support on coping with Thyroid Disorders, please see the recommended organizations, books and Spanish-language resources listed below.
American Academy of Otolaryngology-Head and Neck Surgery Foundation
Website: https://www.entnet.org
Address: 1650 Diagonal Road
Alexandria, VA 22314
Phone: 703-836-4444
American Autoimmune Related Diseases Association (AARDA)
Website: https://www.aarda.org
Address: 22100 Gratiot Avenue
East Detroit, MI 48021
Hotline: 1-800-598-4668
Phone: 586-776-3900
Email: aarda@aarda.org
American Thyroid Association
Website: https://www.thyroid.org
Address: 6066 Leesburg Pike, Suite 550
Falls Church, VA 22041
Hotline: 1-800-THYROID (1-800-849-7643)
Phone: 703-998-8890
Email: thyroid@thyroid.org
Thyroid Federation International
Website: https://www.thyroid-fed.org
Address: P.O. Box 471
Bath, ON K0H 1G0
Email: tfi@thyroid-fed.org
Books
Autoimmune Connection: Essential Information for Women on Diagnosis, Treatment, and Getting On with Your Life
by Rita Baron-Faust and Jill Buyon
Thyroid Balance: Traditional and Alternative Methods for Treating Thyroid Disorders
by Glenn S. Rothfeld and Deborah S. Romaine
Thyroid Power: Ten Steps to Total Health
by Richard Shames and Karilee H. Shames
Thyroid Solution: A Mind-Body Program for Beating Depression and Regaining Your Emotional and Physical Health
by Ridha Arem
Spanish-language resources
Medline Plus: Thyroid Disorders
Website: https://www.nlm.nih.gov/medlineplus/spanish/thyroiddiseases.html
Address: US National Library of Medicine
8600 Rockville Pike
Bethesda, MD 20894
Email: custserv@nlm.nih.gov
American Academy of Family Physicians
Website: https://familydoctor.org/online/famdoces/home/common/hormone/869.printerview.html
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