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Home , Hypothyroidism, Thyroid, Thyroid disease

Hypothyroidism

National Endocrine and Metabolic Diseases Information Service

What is ? Pituitary Hypothyroidism is a disorder that occurs when the gland does not make enough thyroid to meet the U.S. Department of Health and body’s needs. Thyroid hormone regulates Human Services —the way the body uses energy— and affects nearly every in the body. NATIONAL Without enough thyroid hormone, many INSTITUTES OF HEALTH of the body’s functions slow down. About 4.6 percent of the U.S. population age 12 and TSH older has hypothyroidism.1

What is the thyroid? Thyroid The thyroid is a 2-inch-long, butterfly-shaped gland weighing less than 1 ounce. Located in the front of the below the , or voice box, it has two lobes, one on each side T -T of the windpipe. The thyroid is one of the 3 4 that make up the . The glands of the endocrine system produce The thyroid gland makes two thyroid , and store hormones and release them into T3 and T4. Thyroid hormone production is regulated the bloodstream. The hormones then travel by TSH, which is made by the in the through the body and direct the activity of brain. the body’s cells. The thyroid gland makes two thyroid heart and functions, body hormones, (T3) and temperature, muscle strength, skin dryness, thyroxine (T4). T3 is made from T4 and is menstrual cycles, weight, and the more active hormone, directly affecting levels. the tissues. affect Thyroid hormone production is regulated metabolism, brain development, breathing, by thyroid-stimulating hormone (TSH), which is made by the pituitary gland in the brain. When thyroid hormone levels in the blood are low, the pituitary releases more 1Golden SH, Robinson KA, Saldanha I, Anton TSH. When thyroid hormone levels are B, Ladenson PW. Prevalence and incidence of high, the pituitary responds by dropping TSH endocrine and metabolic disorders in the United production. States: a comprehensive review. Journal of Clinical & Metabolism. 2009;94(6):1853–1878. What causes hypothyroidism? Thyroiditis causes stored thyroid hormone Hypothyroidism has several causes, including to leak out of the thyroid gland. At first, the leakage raises hormone levels in the • Hashimoto’s disease blood, leading to —when • thyroiditis, or of the thyroid hormone levels are too high––that thyroid lasts for 1 to 2 months. Most people then develop hypothyroidism before the thyroid is • congenital hypothyroidism, or completely healed. hypothyroidism that is present at birth Several types of thyroiditis can cause • surgical removal of part or all of the hyperthyroidism followed by hypothyroidism: thyroid • . This condition • radiation treatment of the thyroid involves painful inflammation and • some medications enlargement of the thyroid. Experts are not sure what causes subacute Less commonly, hypothyroidism is caused by thyroiditis, but it may be related to too much or too little in the diet or by a viral or bacterial infection. The abnormalities of the pituitary gland. condition usually goes away on its own Hashimoto’s Disease in a few months. Hashimoto’s disease, also called chronic • . This type of lymphocytic thyroiditis, is the most common thyroiditis develops after a woman cause of hypothyroidism in the United gives birth. For more information, see States.1 Hashimoto’s disease is a form of the section titled “What happens with chronic inflammation of the thyroid gland. and thyroid conditions?” Hashimoto’s disease is also an autoimmune • Silent thyroiditis. This type of disorder. thyroiditis is called “silent” because Normally, the protects it is painless, as is postpartum the body against foreign invaders—such thyroiditis, even though the thyroid as viruses and bacteria—that can cause may be enlarged. Like postpartum illness. But in autoimmune diseases, the thyroiditis, silent thyroiditis is probably immune system attacks the body’s own cells an autoimmune condition and and organs. With Hashimoto’s disease, the sometimes develops into permanent immune system attacks the thyroid, causing hypothyroidism. inflammation and interfering with its ability Congenital Hypothyroidism to produce thyroid hormones. Some babies are born with a thyroid More information about Hashimoto’s disease that is not fully developed or does not can be found in the National Endocrine and function properly. If untreated, congenital Metabolic Diseases Information Service hypothyroidism can lead to mental (NEMDIS) fact sheet Hashimoto’s Disease at retardation and growth failure. Early www.endocrine.niddk.nih.gov. treatment can prevent these complications, so most newborns in the United States are screened for hypothyroidism.

2 Hypothyroidism Surgical Removal of the Thyroid What are the symptoms of When part of the thyroid is removed, the hypothyroidism? remaining part may produce normal amounts Hypothyroidism has many symptoms that can of thyroid hormone, but some people who vary from person to person. Some common have this develop hypothyroidism. symptoms of hypothyroidism are Removal of the entire thyroid always results in hypothyroidism. • Part or all of the thyroid may be surgically • removed as a treatment for • a puffy face • hyperthyroidism • cold intolerance • a large goiter, which is an enlarged • and muscle pain thyroid that may cause the neck to appear swollen and can interfere with • normal breathing and swallowing • dry skin • thyroid nodules, which are • dry, thinning hair noncancerous tumors, called , • decreased sweating or lumps in the thyroid that can produce excess thyroid hormone • heavy or irregular menstrual periods and impaired fertility • • Radiation Treatment of the • slowed Thyroid Radioactive iodine, a common treatment However, hypothyroidism develops slowly, for hyperthyroidism, gradually destroys so many people don’t notice symptoms of the the cells of the thyroid. Most people disease. who receive radioactive iodine treatment Symptoms more specific to Hashimoto’s eventually develop hypothyroidism. People disease are a goiter and a feeling of fullness with Hodgkin’s disease, other , in the throat. and head or neck cancers are treated with radiation, which can also damage the thyroid. Hypothyroidism can contribute to high cholesterol, so people with high cholesterol Medications should be tested for hypothyroidism. Rarely, Some drugs can interfere with thyroid severe, untreated hypothyroidism may lead hormone production and lead to to coma, an extreme form of hypothyroidism, including hypothyroidism in which the body’s functions slow to the point that it becomes life • , a heart medication threatening. Myxedema requires immediate • interferon alpha, a cancer medication medical treatment. • , a medication • interleukin-2, a kidney cancer medication

3 Hypothyroidism Who is likely to develop What happens with hypothyroidism? pregnancy and thyroid Women are much more likely than men to conditions? develop hypothyroidism. The disease is also Hypothyroidism. During pregnancy, more common among people older than hypothyroidism is usually caused by 1 age 60. Hashimoto’s disease and occurs in three to Certain factors can increase the chances of five out of every 1,000 .2 developing thyroid disorders. People may Uncontrolled hypothyroidism raises the need more regular testing if they chance of , preterm delivery, and • have had a thyroid problem before, such preeclampsia—a dangerous rise in blood as a goiter pressure during late pregnancy. • have had surgery to correct a thyroid Untreated hypothyroidism during pregnancy problem may also affect the baby’s growth and brain development. Thyroid medications • have received radiation to the thyroid, can help prevent these problems and are neck, or chest safe to take during pregnancy. Women • have a family history of with hypothyroidism should discuss their condition with their provider • have other autoimmune diseases, before becoming pregnant. including – Sjögren’s syndrome, characterized by Postpartum thyroiditis. This inflammation dry eyes and mouth of the thyroid gland affects about 4 to 9 percent of women in the first year after – pernicious , a vitamin B12 giving birth.2 Postpartum thyroiditis is deficiency believed to be an autoimmune condition and – type 1 causes hyperthyroidism that usually lasts for – 1 to 2 months. – , a chronic inflammatory Women with postpartum thyroiditis often condition develop hypothyroidism before the thyroid • have , a genetic gland is completely healed. The condition is disorder that affects females likely to recur with future pregnancies. • are older than age 60 Postpartum thyroiditis sometimes goes • have been pregnant or delivered a baby undiagnosed because the symptoms are within the past 6 months mistaken for postpartum blues—the exhaustion and moodiness that sometimes People should get tested regularly to help follow delivery. If symptoms of fatigue uncover thyroid problems—especially subclinical problems. Subclinical means a person has no apparent symptoms.

2Ogunyemi DA. Autoimmune thyroid disease and pregnancy. emedicine website. http://emedicine. medscape.com/article/261913-overview. Updated March 8, 2012. Accessed February 11, 2013. 4 Hypothyroidism and lethargy do not go away within a few T4 test. This test measures the actual months or if a woman develops postpartum amount of circulating thyroid hormone in the depression, she should talk with her health blood. In hypothyroidism, the level of T4 in care provider. If the hypothyroidism the blood is lower than normal. symptoms are bothersome, thyroid Thyroid test. This test looks medication can be given. for the presence of thyroid . More information can be found in the Most people with Hashimoto’s disease NEMDIS fact sheet Pregnancy and Thyroid have these antibodies, but people whose Disease at www.endocrine.niddk.nih.gov. hypothyroidism is caused by other conditions do not. How is hypothyroidism More information about testing for thyroid diagnosed? problems can be found in the NEMDIS fact sheet at Many symptoms of hypothyroidism are www.endocrine.niddk.nih.gov. the same as those of other diseases, so hypothyroidism usually cannot be diagnosed based on symptoms alone. With suspected How is hypothyroidism hypothyroidism, health care providers take treated? a medical history and perform a thorough Health care providers treat hypothyroidism . Health care providers with synthetic thyroxine, a medication that may then use several blood tests to confirm is identical to the hormone T . The exact a diagnosis of hypothyroidism and find its 4 dose will depend on the patient’s age and cause: weight, the severity of the hypothyroidism, TSH test. The ultrasensitive TSH test is the presence of other health problems, and usually the first test a health care provider whether the person is taking other drugs that performs. This test detects even tiny might interfere with how well the body uses amounts of TSH in the blood and is the thyroid hormone. most accurate measure of thyroid activity Health care providers test TSH levels about available. Generally, a TSH reading above 6 to 8 weeks after a patient begins taking normal means a person has hypothyroidism thyroid hormone and make any necessary and a reading below normal means a person adjustments to the dose. Each time the dose has hyperthyroidism. is adjusted, the blood is tested again. Once Mildly elevated TSH without symptoms a stable dose is reached, blood tests are indicates subclinical hypothyroidism. Some normally repeated in 6 months and then once health care providers treat subclinical a year. hypothyroidism immediately. Others Hypothyroidism can almost always be prefer to leave it untreated but monitor completely controlled with synthetic their patients for signs that the condition is thyroxine, as long as the recommended dose worsening. is taken every day as instructed. Health care providers may conduct additional tests to help confirm the diagnosis or determine the cause of hypothyroidism.

5 Hypothyroidism Eating, Diet, and Nutrition Experts recommend that people eat a Points to Remember balanced diet to obtain most nutrients. More • Hypothyroidism is a disorder that information about diet and nutrition can be occurs when the thyroid gland does found on the National Agricultural Library not make enough thyroid hormone website at www.nutrition.gov. to meet the body’s needs. Thyroid hormone regulates metabolism. Dietary Supplements Without enough thyroid hormone, Iodine is an essential mineral for the thyroid. many of the body’s functions slow However, people with autoimmune thyroid down. disease may be sensitive to harmful side • Hypothyroidism has several causes, effects from iodine. Taking iodine drops including or eating containing large amounts of iodine—such as seaweed, dulse, or – Hashimoto’s disease kelp—may cause or worsen hypothyroidism – thyroiditis or hyperthyroidism. More information – congenital hypothyroidism about iodine can be found in the National – surgical removal of part or all of Library of Medicine fact sheet Iodine in the thyroid diet, available at http://www.nlm.nih.gov/ /ency/article/002421.htm. – radiation treatment of the thyroid Women need more iodine when they are – some medications pregnant—about 250 micrograms a day— because the baby gets iodine from the • Hypothyroidism has many mother’s diet. In the United States, about symptoms that can vary from 7 percent of pregnant women may not person to person. Some common get enough iodine in their diet or through symptoms of hypothyroidism prenatal vitamins.3 Choosing iodized — are fatigue, weight gain, cold salt supplemented with iodine—over plain intolerance, constipation, impaired salt and prenatal vitamins containing iodine fertility, and depression. will ensure this need is met. • Women are much more likely than To help ensure coordinated and safe care, men to develop hypothyroidism. people should discuss their use of dietary • Women with hypothyroidism supplements, such as iodine, with their health should discuss their condition with care provider. Tips for talking with health their health care provider before care providers can be found on the National becoming pregnant. Center for Complementary and Alternative • Hypothyroidism can almost always Medicine’s Time to Talk campaign website at be completely controlled with www.nccam.nih.gov/timetotalk. synthetic thyroxine, as long as the recommended dose is taken every day as instructed.

3Zimmerman MB. in pregnancy and the effects of maternal iodine supplementation on the offspring: a review. American Journal of Clinical Nutrition. 2009;89(2):668S–672S. 6 Hypothyroidism Hope through Research For More Information The National Institute of Diabetes and American Academy of Otolaryngology— Digestive and Kidney Diseases (NIDDK) Head and Neck Surgery conducts and supports research into 1650 Diagonal Road many kinds of disorders, including Alexandria, VA 22314–2857 hypothyroidism. Researchers throughout Phone: 703–836–4444 the United States and the world are working Internet: www.entnet.org to better understand, prevent, and treat American Association of Clinical this disease. Researchers are investigating Endocrinologists the development, , 245 Riverside Avenue, Suite 200 and genetics of thyroid function disorders Jacksonville, FL 32202 to further understand thyroid diseases. Phone: 904–353–7878 Scientists continue to study treatment Fax: 904–353–8185 options for hypothyroidism and other thyroid Internet: www.aace.com disorders. American Thyroid Association Clinical trials are research studies involving 6066 Leesburg Pike, Suite 550 people. Clinical trials look at safe and Falls Church, VA 22041 effective new ways to prevent, detect, or Phone: 1–800–THYROID (1–800–849–7643) treat disease. Researchers also use clinical or 703–998–8890 trials to look at other aspects of care, such Fax: 703–998–8893 as improving the quality of life for people Email: [email protected] with chronic illnesses. To learn more about Internet: www.thyroid.org clinical trials, why they matter, and how to participate, visit the NIH Clinical Research Hormone Health Network Trials and You website at www.nih.gov/health/ 8401 Connecticut Avenue, Suite 900 clinicaltrials. For information about current Chevy Chase, MD 20815–5817 studies, visit www.ClinicalTrials.gov. Phone: 1–800–HORMONE (1–800–467–6663) Fax: 301–941–0259 Email: [email protected] Internet: www.hormone.org The Endocrine Society 8401 Connecticut Avenue, Suite 900 Chevy Chase, MD 20815 Phone: 1–888–363–6274 or 301–941–0200 Fax: 301–941–0259 Email: [email protected] Internet: www.endo-society.org

7 Hypothyroidism Acknowledgments National Endocrine Publications produced by the NIDDK are and Metabolic Diseases carefully reviewed by both NIDDK scientists Information Service and outside experts. This publication was originally reviewed by Leonard Wartofsky, 6 Information Way M.D., M.A.C.P., Washington Hospital Bethesda, MD 20892–3569 Center, and Nabeel Babar, M.D., NIDDK. Phone: 1–888–828–0904 TTY: 1–866–569–1162 Fax: 703–738–4929 Email: [email protected] You may also find additional information about this topic by visiting MedlinePlus at www.medlineplus.gov. Internet: www.endocrine.niddk.nih.gov This publication may contain information about The National Endocrine and Metabolic medications and, when taken as prescribed, the conditions they treat. When prepared, this publica- Diseases Information Service is an tion included the most current information available. information dissemination service of the For updates or for questions about any medications, National Institute of Diabetes and Digestive contact the U.S. and Drug Administration toll- free at 1–888–INFO–FDA (1–888–463–6332) or visit and Kidney Diseases (NIDDK). The www.fda.gov. Consult your health care provider for NIDDK is part of the National Institutes of more information. Health, which is part of the U.S. Department of Health and Human Services. The NIDDK conducts and supports biomedical research. As a public service, the NIDDK has established information services to increase knowledge and understanding about health and disease among patients, health professionals, and the public.

This publication is not copyrighted. The NIDDK encourages users of this publication to duplicate and distribute as many copies as desired. This publication is available at www.endocrine.niddk.nih.gov.

U.S. DEPARTMENT OF HEALTH AND HUMAN SERVICES National Institutes of Health NIH...Turning Discovery Into Health®

NIH Publication No. 13–6180 March 2013

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