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Hypothyroidism is a condition in which the thyroid gland does not produce enough thyroid hormone. Thyroid hormone is made by the thyroid gland which is a butterfly-shaped gland in the front of the neck. It produces the hormones thyroxine (T4) and triiodothyronine (T3), which control metabolism. This affects how many calories you burn, how warm you feel, how much you weigh, and how the bodies handles many other vital functions of the cardiovascular, gastrointestinal, and nervous systems. Hypothyroidism results in a slower metabolism and slower heartbeat.
The Thyroid Gland |
The most common form of hypothyroidism is Hashimoto’s thyroiditis. This condition occurs when your immune system produces antibodies that attack the cells of the thyroid gland, resulting in chronic thyroid inflammation and destruction, resulting in the loss of thyroid function. After Hashimoto’s thyroiditis, the other less common causes include hypothyroidism as a result of neck radiation for lymphoma and treatment of hyperthyroidism or thyroid cancer with radioactive iodine or surgery.
Other causes of hypothyroidism include:
- Subacute thyroiditis—This occurs when there is inflammation of the thyroid gland following a viral upper respiratory tract infection.
- Drugs—Drugs used to treat hyperthyroidism, lithium (used to treat certain psychiatric disorders), certain cardiac medicines, and other medicines (tumor necrosis factor, interleukins, alpha interferon) can cause this condition.
- Medical treatments—Treatments include radiation or surgical removal of part of the thyroid gland (called subtotal thyroidectomy) for the treatment of other thyroid diseases.
- Idiopathic thyroid atrophy—The thyroid tissue shrivels up (atrophies) for unknown reasons.
- Iodine deficiency—This occurs when a thyroid gland does not get enough iodine to produce thyroid hormone (this is rare in the United States)
- Iodine excess—Certain foods (such as shellfish) and certain medicines (such as cough medicine) contain large amounts of iodine, which can ultimately block thyroid hormone production. This is also rare.
- Infiltrative illnesses—These include cancers and certain infections.
- Pituitary adenoma—This is a benign tumor of the pituitary gland that can cause a problem signaling the thyroid to make thyroid hormone.
- Postpartum thyroiditis—This condition usually improves without treatment but may persist.
- Chronic thyroiditis—This usually occurs after hyperthyroidism.
About 5% of Americans have hypothyroidism. This condition usually occurs in adults. But, in some cases, children or infants may have hypothyroidism (called cretinism ). Children require treatment as quickly as possible or mental retardation may result.
What are the risk factors of hypothyroidism?
[What are the symptoms of hypothyroidism?
[How is hypothyroidism diagnosed?
What are the treatments for hypothyroidism?
Are there screening tests for hypothyroidism?
[How can I reduce my risk of hypothyroidism?
References:
American Medical Women’s Association website. Available at: http://www.amwa-doc.org/ .
American Thyroid Association website. Available at: http://www.thyroid.org/ .
Garber JR, Hennessey JV, Liebermann JA, Morris CM. Clinical update. Managing the challenges of hypothyroidism. J Fam Pract.2006;55:S1-8.
Harrison’s Principles of Internal Medicine.15th ed. Mc-Graw-Hill; 2001.
National Endocrine and Metabolic Diseases Information Service. Hypothyroidism. National Endocrine and Metabolic Diseases Information Service website. Available at: http://endocrine.niddk.nih.gov/pubs/Hypothyroidism/ . Updated May 2008. Accessed August 2, 2010.
Vanderpump MPJ, Tunbridge WMG, French JM, et al. The incidence of thyroid disorders in the community: a twenty-year follow-up of the Whickham survey. Clin Endocrinol.1995; 43:55.
References:
American Association of Clinical Endocrinologists website. Available at: http://www.aace.com/ .
Harrison's Principles of Internal Medicine.15th ed. McGraw-Hill; 2001.
References:
American Thyroid Association website. Available at: http://www.thyroid.org/ .
Harrison's Principles of Internal Medicine.15th ed. McGraw-Hill; 2001.
Roberts CG, Ladenson RW. Hypothyoidism. Lancet.2004;363:793-803.
Hypothyroidism is a condition in which the thyroid gland does not produce enough thyroid hormone. Thyroid hormone is made by the thyroid gland which is a butterfly-shaped gland in the front of the neck. It produces the hormones thyroxine (T4) and triiodothyronine (T3), which control metabolism. This affects how many calories you burn, how warm you feel, how much you weigh, and how the bodies handles many other vital functions of the cardiovascular, gastrointestinal, and nervous systems. Hypothyroidism results in a slower metabolism and slower heartbeat.
The Thyroid Gland |
The most common form of hypothyroidism is Hashimoto’s thyroiditis. This condition occurs when your immune system produces antibodies that attack the cells of the thyroid gland, resulting in chronic thyroid inflammation and destruction, resulting in the loss of thyroid function. After Hashimoto’s thyroiditis, the other less common causes include hypothyroidism as a result of neck radiation for lymphoma and treatment of hyperthyroidism or thyroid cancer with radioactive iodine or surgery.
Other causes of hypothyroidism include:
- Subacute thyroiditis—This occurs when there is inflammation of the thyroid gland following a viral upper respiratory tract infection.
- Drugs—Drugs used to treat hyperthyroidism, lithium (used to treat certain psychiatric disorders), certain cardiac medicines, and other medicines (tumor necrosis factor, interleukins, alpha interferon) can cause this condition.
- Medical treatments—Treatments include radiation or surgical removal of part of the thyroid gland (called subtotal thyroidectomy) for the treatment of other thyroid diseases.
- Idiopathic thyroid atrophy—The thyroid tissue shrivels up (atrophies) for unknown reasons.
- Iodine deficiency—This occurs when a thyroid gland does not get enough iodine to produce thyroid hormone (this is rare in the United States)
- Iodine excess—Certain foods (such as shellfish) and certain medicines (such as cough medicine) contain large amounts of iodine, which can ultimately block thyroid hormone production. This is also rare.
- Infiltrative illnesses—These include cancers and certain infections.
- Pituitary adenoma—This is a benign tumor of the pituitary gland that can cause a problem signaling the thyroid to make thyroid hormone.
- Postpartum thyroiditis—This condition usually improves without treatment but may persist.
- Chronic thyroiditis—This usually occurs after hyperthyroidism.
About 5% of Americans have hypothyroidism. This condition usually occurs in adults. But, in some cases, children or infants may have hypothyroidism (called cretinism ). Children require treatment as quickly as possible or mental retardation may result.
What are the risk factors of hypothyroidism?
What are the symptoms of hypothyroidism?
How is hypothyroidism diagnosed?
What are the treatments for hypothyroidism?
Are there screening tests for hypothyroidism?
How can I reduce my risk of hypothyroidism?
A risk factor is something that increases your likelihood of getting a disease or condition.
It is possible to develop hypothyroidism with or without the risk factors listed below. However, the more risk factors you have, the greater your likelihood of developing hypothyroidism. If you have a number of risk factors, ask your healthcare provider what you can do to reduce your risk.
Medical Conditions
There are several medical conditions known to increase your risk of hypothyroidism. These include:
- Pregnancy—Five to eight percent of women develop postpartum thyroiditis. This condition is characterized by hyperthyroidism that is followed by hypothyroidism. Improvement usually results without treatment, but recurrences can occur and treatment is sometimes needed. This condition can also overlap with other causes of hyper or hypothyroidism.
- A history of other autoimmune diseases, such as:
- Pernicious anemia
- Type 1 diabetes
- Underactive adrenal or parathyroid glands
- Rheumatoid arthritis
- Lupus
- Sjogren’s syndrome
- Addison’s disease
- Celiac disease
- Myaesthenia gravis
Age
Your risk of hypothyroidism increases with age, especially after age 65 years.
Gender
Women are approximately 4 to 5 times more likely to develop the condition than men.
Genetic factors
If any of your family members have hypothyroidism, you are at greater risk.
Race/Ethnicity
Hypothyroidism occurs more often in Caucasians than in African Americans.
References:
American Association of Clinical Endocrinologists website. Available at: http://www.aace.com/ .
American Thyroid Association website. Available at: http://www.thyroid.org/ .
Harrison’s Principles of Internal Medicine.14th ed. McGraw-Hill; 2002.
Singer P, Cooper D, Levy E, et al. Treatment guidelines for patients with hyperthyroidism and hypothyroidism. JAMA. 1995;273:808-812.
Wartofsky L. Myxedema coma. Endocrinol Metab Clin North Am.2006;35:687-98.
References:
American Association of Clinical Endocrinologists website. Available at: http://www.aace.com/ .
Fatourechi V.Subclinical Hypothyroidism: An Update for Primary Care Physicians. Mayo Clin Proc. January 1, 2009 84:65-71
Harrison's Principles of Internal Medicine.15th ed. McGraw-Hill; 2001.
Thyroid Foundation of Canada website. Available at: http://www.thyroid.ca/ .
Surks MI, Ortiz E, Daniels GH, et al. Subclinical thyroid disease: scientific review and guidelines for diagnosis and management. JAMA.2004;291:228-38.
Symptoms usually come on gradually, over weeks or months. Therefore, you may have hypothyroidism for a long time, even years, before you realize you are ill. If you are an older adult, it may be even harder to recognize you are ill because instead of getting the typical symptoms of hypothyroidism, you may just gain weight or feel tired. Symptoms vary with the severity of the hypothyroidism and the length of time your body has lacked the proper amount of thyroid hormone.
You may have only one of these symptoms, but usually patients have a combination. Occasionally, patients with hypothyroidism have no symptoms at all, or the symptoms are so subtle they go unnoticed for a long period of time.
Symptoms include:
- Enlargement of the thyroid gland, called goiter (not always present)
- Fullness in the neck
- Difficulty swallowing or trouble breathing (can happen if the goiter is very large)
Thyroid |
Later symptoms or signs include:
- Fatigue
- Weakness
- Coarse, brittle hair and hair loss
- Dry, scaly skin
- Intolerance to cold temperatures
- Weight gain (may happen despite having a poor appetite)
- Constipation
- Achy feeling all over
- Depression and irritability
- Memory loss and personality change
- Irregular or heavy menstrual periods
- Orange palms and soles (hypercarotenemia)
- Facial puffiness
- Swollen feet or hands
- Numbness and tingling of extremities
- Infertility
- Reduced sweating
- Sleep apnea
Symptoms of severe or prolonged cases include:
- Diffuse swelling of the skin and tissue around the eyes
- Slow heart rate
- Hypothermia (low body temperature)
- Hoarseness
- Shortness of breath during exertion or when lying flat
- Lethargy and mental decline
The doctor will perform a physical exam and ask about your symptoms and medical/family history. Hypothyriodism is often found in families. The exam may reveal a goiter (enlarged thyroid), slow reflexes, dry skin, slow and hoarse speech, and/or a large tongue.
Your doctor may also do the following tests:
Blood Tests—Blood tests measure the level of thyroid hormones and thyroid antibodies. The diagnosis of hypothyroidism is made if the serum level of thyroid stimulating hormone (TSH) is elevated, and if the levels of serum free T4 (free thyroxine), and sometimes total T3, are low. These results mean that the thyroid gland is not making enough thyroid hormone.
The presence of thyroid antibodies may also signal autoimmune hypothyroidism, such as Hashimoto's thyroiditis, but is not needed for the diagnosis of hypothyroidism. The most common cause of hypothyroidism is autoimmune thyroiditis (Hashimotos).
Some blood tests performed for other reasons may raise suspicions about hypothyroidism and should be followed up, for example, blood tests that show high cholesterol, anemia, or low sodium.
References:
American Association of Clinical Endocrinologists website. Available at: http://www.aace.com/ .
David Sarne, Chapter 5a. Effects of the Environment, Chemicals and Drugs on Thyroid Function. Endotext, available at endotext.com. Published October 11, 2007. Accessed July 30, 2010.
Harrison's Principles of Internal Medicine. 15th ed. McGraw-Hill; 2001.
Roberts CG, Ladenson RW. Hypothyroidism. Lancet. 2004;363:793-803.
Trumbo PR. Perchlorate consumption, iodine status, and thyroid function. Nutr Rev. 2010; 68(1):62-6.
Several drugs may cause hypothyroidism, but the association is not definitive. Some examples are:
- Perchlorate
- Lithium
- Thionamides
- Sulfonamides
- Ketoconazole
- Large doses of iodine
- Interleukin II
- Interferon
- Sunitinib
Although rare in the United States, iodine deficiency can cause hypothyroidism. A varied American diet and the use of iodized salt can avoid this nutritional deficiency. Your doctor or a registered dietitian can help you to identify foods rich in iodine, such as shellfish, iodized salt, breads, and cereals.
References:
American Academy of Pediatrics. Update of newborn screening and therapy for congenital hypothyroidism. Pediatrics. 2006;117:2290-2303.
American Association of Clinical Endocrinologists website. Available at: http://www.aace.com/ .
American College of Obstetricians and Gynecologists website. Available at: http://www.acog.org/ .
The American College of Physicians website. Available at: http://www.acponline.org/ .
Cooper DS, Doherty GM, Haugen BR, Kloos RT, Lee SL, Mandel SJ et al. Thyroid. November 2009;19(11):1167-1214.
National Guideline Clearinghouse website. Available at: http://www.guideline.gov/ .
Ladenson P, Singer P, Kenneth B, et al. American Thyroid Association Guidelines for Detection of Thyroid Dysfunction. Arch Intern Med. 2000;160:1573-1575.
Surks MI, Ortiz E, Daniels GH, et al. Subclinical thyroid disease: scientific review and guidelines for diagnosis and management. JAMA. 2004 Jan 14;291(2):228-38.
The United States Preventive Services Task Force. Screening for thyroid disease: recommendation statement. Ann Intern Med. 2004;140:125-127
American Association of Clinical Endocrinologists (AACE)
Address:
245 Riverside AVE, STE 200
Jacksonville, FL 32204
Internet address:
http://www.aace.com
Description of services provided:
This organization, the primary professional association for practicing endocrinologists, with over 5,200 members worldwide, offers resources for the public and professionals.
American Thyroid Association
Address:
6066 Leesburg Pike, Suite 550
Falls Church, VA. 22041
Internet address:
http://www.thyroid.org
Description of services provided:
This is an official site for both patients and professionals of the highly respected and authoritarian organization. There are information sheets for patients, lists of recommended books, and lists of support organizations.
EndocrineWeb.com
Internet address:
http://www.endocrineweb.com
Description of services provided:
EndocrineWeb covers all the glands of the body. The site provides thorough overviews with attractive illustrations to clarify the material. You can also share information in the chat room.
Hormone.org
Internet address:
http://www.hormone.org
Description of services provided:
Patient-centered information from leading authorities from the Endocrine Society.
Mythyroid.com
Internet address:
http://www.mythyroid.com
Description of services provided:
Evidenced-based, patient-centered information collected and organized by Dr. Daniel Drucker, University of Toronto.
The purpose of screening is early diagnosis and treatment. Screening tests are usually administered to people without current symptoms, but who may be at high risk for certain diseases or conditions. Screening for hypothyroidism remains controversial due to the lack of definite evidence for a benefit.
Screening Tests
A physical exam by your doctor may reveal signs of hypothyroidism, such as dry skin, a slow pulse, or slowed reflexes. A thorough history may reveal symptoms of weight gain, fatigue, and constipation.
The best screening test is a blood test that measures thyroid-stimulating hormone (TSH). A high level of TSH suggests hypothyroidism. If this is found to be elevated, your doctor may order other a free thyroxine (FT4).
Screening Guidelines
The United States Preventive Services Task Force found insufficient evidence to recommend for or against routine screening for thyroid disease. It is recommended for the following high-risk groups:
- All newborn infants (mandatory in many states)
- Downs syndrome
- Pregnant women with or without goiter
- Have a strong family history of thyroid disease
- A personal history of thyroid dysfunction
- Have an autoimmune disease, such as type 1 diabetes
- Are taking lithium
- Have depression
- Have elevated lipid levels
- Are found to have a thyroid nodule
Several other professional organizations such as the American Association of Clinical Endocrinologist (AACE), American Academy of Family Physicians (AAFP), The American College of Physician (ACP) and the American Thyroid Association (ATA) vary greatly in their recommendations with the ATA recommending routine screening at age 35 then every five years. High risk populations can include those:
- Over 60 years old
- With a history of thyroid disease, thyroid surgery, radiation to the neck
- With a heart disease history, specifically atrial fibrillation
- With other autoimmune disease
You have a unique medical history. Therefore, it is essential to talk with your doctor about your personal risk factors and/or experience with hypothyroidism. By talking openly and regularly with your doctor, you can take an active role in your care.
General Tips for Gathering Information
Here are some tips that will make it easier for you to talk to your doctor:
- Bring someone else with you. It helps to have another person hear what is said and think of questions to ask.
- Write out your questions ahead of time, so you don't forget them.
- Write down the answers you get, and make sure you understand what you are hearing. Ask for clarification, if necessary.
- Don't be afraid to ask your questions or ask where you can find more information about what you are discussing. You have a right to know.
If available, bring all previous records of radiology (thyroid ultrasounds, nuclear medicine thyroid scan and/or uptake), lab tests of thyroid function, and treatments. Plan ahead to contact previous doctors to collect and gather this information to bring it with you. Bring a current medication list with name and dose.
Specific Questions to Ask Your Doctor
About Other Medical Problems
- Could my hypothyroidism be caused by another, more significant health problem?
- Will hypothyroidism lead to any further health problems for me?
- Could my hypothyroidism be passed on to my children?
About Treatment
- Which hormones will I need to take?
- Are there any symptoms or dangerous side effects that I should report to you?
- How soon after I begin treatment can I expect to have a normal level of thyroid hormone?
- How will I know if my level of thyroid hormone is stable?
- How soon will I start to feel better?
- Will synthetic hormones interact with any other medications or dietary supplements that I'm taking for other conditions?
- Is it safe for me to get pregnant and breastfeed while taking these hormones? Will I need a change in my medicine dosage during pregnancy?
- Are there any other treatment options? What about alternative and complementary approaches to treatment?
- Do I need to worry about gaining weight? Can you refer me to a registered dietitian or someone who can help me to control my weight?
- Should I take my thyroid pill with food or on an empty stomach?
- Does it matter if I take my thyroid pill in the morning or at night before bed?
About Outlook
- What is the possibility of my thyroid returning to normal function?
- How often do I need to see the doctor for follow-up care after my thyroid hormone level is normal?
- Will I gain weight?
