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Hypothyroidism, or underactive thyroid, develops when the thyroid gland fails to produce or secrete as much thyroxine (T4) as the body needs. Because T4 regulates such essential functions as heart rate, digestion, physical growth, and mental development, an insufficient supply of this hormone can slow life-sustaining processes, damage organs and tissues in every part of the body, and lead to life-threatening complications.


Hypothyroidism is one of the most common chronic diseases in the United States. Symptoms may not appear until years after the thyroid has stopped functioning and they are often mistaken for signs of other illnesses, menopause, or aging. Although this condition is believed to affect as many as 11 million adults and children, as many as two of every three people with hypothyroidism may not know they have the disease.
Nicknamed "Gland Central" because it influences almost every organ, tissue, and cell in the body, the thyroid is shaped like a butterfly and located just below the Adam's apple. The thyroid stores iodine the body gets from food and uses this mineral to create T4. Low T4 levels can alter weight, appetite, sleep patterns, body temperature, sex drive, and a variety of other physical, mental, and emotional characteristics.
There are three types of hypothyroidism. The most common is primary hypothyroidism, in which the thyroid doesn't produce an adequate amount of T4. Secondary hypothyroidism develops when the pituitary gland does not release enough of the thyroid-stimulating hormone (TSH) that prompts the thyroid to manufacture T4. Tertiary hypothyroidism results from a malfunction of the hypothalamus, the part of the brain that controls the endocrine system. Drug-induced hypothyroidism, an adverse reaction to medication, occurs in two of every 10,000 people, but rarely causes severe hypothyroidism.
Hypothyroidism is at least twice as common in women as it is in men. Although hypothyroidism is most common in women who are middle-aged or older, the disease can occur at any age. Newborn infants are tested for congenital thyroid deficiency (cretinism) using a test that measures the levels of thyroxine in the infant's blood. Treatment within the first few months of life can prevent mental retardation and physical abnormalities. Older children who develop hypothyroidism suddenly stop growing.
Factors that increase a person's risk of developing hypothyroidism include age, weight, and medical history. Women are more likely to develop the disease after age 50; men, after age 60. Obesity also increases risk. A family history of thyroid problems or a personal history of high cholesterol levels or such autoimmune diseases as lupus, rheumatoid arthritis, or diabetes can make an individual more susceptible to hypothyroidism.

Causes and symptoms

Hypothyroidism is most often the result of Hashimoto's disease, also known as chronic thyroiditis (inflammation of the thyroid gland). In this disease, the immune system fails to recognize that the thyroid gland is part of the body's own tissue and attacks it as if it were a foreign body. The attack by the immune system impairs thyroid function and sometimes destroys the gland. Other causes of hypothyroidism include:
  • Radiation. Radioactive iodine used to treat hyperthyroidism (overactive thyroid) or radiation treatments for head or neck cancers can destroy the thyroid gland.
  • Surgery. Removal of the thyroid gland because of cancer or other thyroid disorders can result in hypothyroidism.
  • Viruses and bacteria. Infections that depress thyroid hormone production usually cause permanent hypothyroidism.
  • Medication. Nitroprusside, lithium, or iodides can induce hypothyroidism. Because patients who use these medications are closely monitored by their doctors, this side effect is very rare.
  • Pituitary gland malfunction. This is a rare condition in which the pituitary gland fails to produce enough TSH to activate the thyroid's production of T4.
  • Congenital defect. One of every 4,000 babies is born without a properly functioning thyroid gland.
  • Diet. Because the thyroid makes T4 from iodine drawn from food, an iodine-deficient diet can cause hypothyroidism. Adding iodine to table salt and other common foods has eliminated iodine deficiency in the United States. Certain foods (cabbage, rutabagas, peanuts, peaches, soybeans, spinach) can interfere with thyroid hormone production.
  • Environmental contaminants. Certain man-made chemicals—such as PCBs—found in the local environment at high levels may also cause hypothyroidism.
Hypothyroidism is sometimes referred to as a "silent" disease because early symptoms may be so mild that no one realizes anything is wrong. Untreated symptoms become more noticeable and severe, and can lead to confusion and mental disorders, breathing difficulties, heart problems, fluctuations in body temperature, and death.
Someone who has hypothyroidism will probably have more than one of the following symptoms:
  • fatigue
  • decreased heart rate
  • progressive hearing loss
  • weight gain
  • problems with memory and concentration
  • depression
  • goiter (enlarged thyroid gland)
  • muscle pain or weakness
  • loss of interest in sex
  • numb, tingling hands
  • dry skin
  • swollen eyelids
  • dryness, loss, or premature graying of hair
  • extreme sensitivity to cold
  • constipation
  • irregular menstrual periods
  • hoarse voice
Hypothyroidism usually develops gradually. When the disease results from surgery or other treatment for hyperthyroidism, symptoms may appear suddenly and include severe muscle cramps in the arms, legs, neck, shoulders, and back.
It's important to see a doctor if any of these symptoms appear unexpectedly. People whose hypothyroidism remains undiagnosed and untreated may eventually develop myxedema. Symptoms of this rare but potentially deadly complication include enlarged tongue, swollen facial features, hoarseness, and physical and mental sluggishness.
Myxedema coma can cause unresponsiveness; irregular, shallow breathing; and a drop in blood pressure and body temperature. The onset of this medical emergency can be sudden in people who are elderly or have been ill, injured, or exposed to very cold temperatures; who have recently had surgery; or who use sedatives or anti-depressants. Without immediate medical attention, myxedema coma can be fatal.


Diagnosis of hypothyroidism is based on the patient's observations, medical history, physical examination, and thyroid function tests. Doctors who specialize in treating thyroid disorders (endocrinologists) are most apt to recognize subtle symptoms and physical indications of hypothyroidism. A blood test known as a thyroid-stimulating hormone (TSH) assay, thyroid nuclear medicine scan, and thyroid ultrasound are used to confirm the diagnosis. A woman being tested for hypothyroidism should let her doctor know if she is pregnant or breastfeeding and all patients should be sure their doctors are aware of any recent procedures involving radioactive materials or contrast media.
The TSH assay is extremely accurate, but some doctors doubt the test's ability to detect mild hypothyroidism. They advise patients to monitor their basal (resting) body temperature for below-normal readings that could indicate the presence of hypothyroidism.


Natural or synthetic thyroid hormones are used to restore normal (euthyroid) thyroid hormone levels. Synthetic hormones are more effective than natural substances, but it may take several months to determine the correct dosage. Patients start to feel better within 48 hours, but symptoms will return if they stop taking the medication.
Most doctors prescribe levothyroxine sodium tablets, and most people with hypothyroidism will take the medication for the rest of their lives. Aging, other medications, and changes in weight and general health can affect how much replacement hormone a patient needs, and regular TSH tests are used to monitor hormone levels. Patients should not switch from one brand of thyroid hormone to another without a doctor's permission.
Regular exercise and a high-fiber diet can help maintain thyroid function and prevent constipation.

Alternative treatment

Alternative treatments are primarily aimed at strengthening the thyroid and will not eliminate the need for thyroid hormone medications. Herbal remedies to improve thyroid function and relieve symptoms of hypothyroidism include bladder wrack (Fucus vesiculosus), which can be taken in capsule form or as a tea. Some foods, including cabbage, peaches, radishes, soybeans, peanuts, and spinach, can interfere with the production of thyroid hormones. Anyone with hypothyroidism may want to avoid these foods. The Shoulder Stand yoga position (at least once daily for 20 minutes) is believed to improve thyroid function.


Thyroid hormone replacement therapy generally maintains normal thyroid hormone levels unless treatment is interrupted or discontinued.


Primary hypothyroidism can't be prevented, but routine screening of adults could detect the disease in its early stages and prevent complications.

Key terms

Cretinism — Severe hypothyroidism that is present at birth.
Endocrine system — The network of glands that produce hormones and release them into the bloodstream. The thyroid gland is part of the endocrine system.
Hypothalamus — The part of the brain that controls the endocrine system.
Myxedema — A condition that can result from a thyroid gland that produces too little of its hormone. In addition to a decreased metabolic rate, symptoms may include anemia, slow speech, an enlarged tongue, puffiness of the face and hands, loss of hair, coarse and thickened skin, and sensitivity to cold.
Pituitary gland — Small, oval endocrine gland attached to the hypothalamus. The pituitary gland releases TSH, the hormone that activates the thyroid gland.
Thyroid-stimulating hormone (TSH) — A hormone secreted by the pituitary gland that controls the release of T4 by the thyroid gland.
Thyroxine (T 4 ) — Thyroid hormone that regulates many essential body processes.



American Thyroid Association. Montefiore Medical Center, 111 E. 210th St., Bronx, NY 10467.
Endocrine Society. 4350 East West Highway, Suite 500, Bethesda, MD 20814-4410. (301) 941-0200.
Thyroid Foundation of America, Inc. Ruth Sleeper Hall, RSL 350, Boston, MA 02114-2968. (800) 832-8321 or (617) 726-8500.
Thyroid Society for Education and Research. 7515 S. Main St., Suite 545, Houston, TX 77030. (800) THYROID or (713) 799-9909.
Gale Encyclopedia of Medicine. Copyright 2008 The Gale Group, Inc. All rights reserved.


deficiency of thyroid gland activity, with underproduction of thyroxine, or the condition resulting from it. In its severe form it is called myxedema and is characterized by physical and mental sluggishness, obesity, loss of hair, enlargement of the tongue, and thickening of the skin. In children the condition is known as cretinism. Called also athyria. adj., adj hypothy´roid.
pituitary hypothyroidism secondary hypothyroidism caused by a defect or lesion of the pituitary gland that interferes with production of thyrotropin; the majority of cases are caused by tumors.
primary hypothyroidism hypothyroidism due to disease of the thyroid gland itself, usually accompanied by increased levels of thyrotropin.
secondary hypothyroidism that caused by thyrotropin deficiency.
Miller-Keane Encyclopedia and Dictionary of Medicine, Nursing, and Allied Health, Seventh Edition. © 2003 by Saunders, an imprint of Elsevier, Inc. All rights reserved.


Diminished production of thyroid hormone, leading to clinical manifestations of thyroid insufficiency, including low metabolic rate, tendency to gain weight, somnolence, and sometimes myxedema.
Synonym(s): athyrea (1)
[hypo- + G. thyreoeidēs, thyroid]
Farlex Partner Medical Dictionary © Farlex 2012


1. Insufficient production of thyroid hormones.
2. Insufficient functioning of the thyroid gland.
The American Heritage® Medical Dictionary Copyright © 2007, 2004 by Houghton Mifflin Company. Published by Houghton Mifflin Company. All rights reserved.


Endocrinology A condition characterized by underproduction of thyroid hormones Clinical Fatigue, hypersomnolence Diagnosis Serum TSH. See Central hypothyroidism, Primary hyperthyroidism, Secondary hypothyroidism. Cf Hyperthyroidism.
McGraw-Hill Concise Dictionary of Modern Medicine. © 2002 by The McGraw-Hill Companies, Inc.


Diminished production of thyroid hormone, leading to clinical manifestations of thyroid insufficiency, including somnolence, slow mentation, dryness and loss of hair, subnormal temperature, hoarseness, muscle weakness, delayed relaxation of tendon reflexes, and sometimes myxedema.
[hypo- + G. thyreoeidēs, thyroid]
Medical Dictionary for the Health Professions and Nursing © Farlex 2012


Underactivity of the THYROID GLAND. See MYXOEDEMA.
Collins Dictionary of Medicine © Robert M. Youngson 2004, 2005


a condition caused by a deficiency of thyroid hormone and the underactivity of the thyroid gland. It results in mental deficiency.
Collins Dictionary of Biology, 3rd ed. © W. G. Hale, V. A. Saunders, J. P. Margham 2005


Diminished production of thyroid hormone, leading to clinical manifestations of thyroid insufficiency.
[hypo- + G.thyreoeidēs, thyroid]
Medical Dictionary for the Dental Professions © Farlex 2012

Patient discussion about hypothyroidism

Q. What Are the Symptoms of Hypothyroidism? My friend suffers from hypothyroidism. I have been feeling tired lately and she told me I should get examined too. What are the symptoms of this disease?

A. It's true that these symptoms are also common with other conditions, so it's always important to talk to your doctor about it or any noticeable changes; mental fatigue and depression can also occur and the tiredness can range from unusual lack of energy to just plain exhaustion. Bloodwork will need to be done to determine if you have low hormone levels and subsequent follow-ups will be needed to determine the correct dosage. Hormone replacement will most likely have to be continued for the rest your life, so ask your doctor what the best options are.

Try some exercise or weight loss first: you should feel an initial burst of energy and lose weight in a typical fashion, but with hypothyroidism, you may experience a crash in energy, mental dullness, and ability to lose weight.

Q. Hi Everyone, my name is Selly with Bipolar. Are there homeopathic meds for Hypothyroidism and Bipolar?

A. Hi, I also have hypothyroidism along with my bipolar depression. I would agree with Dagmar that getting some conventional medical treatment first is the right way to go. I certainly wouldn't knock a homeopathic treatment that worked, but for bipolar disorder you really should be monitored closely by a doctor. Perhaps you can integrate some homeopathic remedies with your conventional medications, under the observation of a doctor, of course. Good luck, and if you find something that works for you let us know!

Q. Is their a drug available to regain my energy back from having hypothyrodiam? I was diagnosed three years ago with Hypothyroidism. I have been using medication to level out my thyroid level. The lack of energy and weakness I am experiencing at the age of 42 is maddening. I want my life back the way it was. I am tired of feeling tired and zombie like.

A. Hormone replacement has to be continued throughout your life; Zoe is probably right: you may need a higher dose. Talk to your doctor about the fatigue, you should have regular check-ups again to monitor your hormone levels to get the right dosage.

You can always ask for more information about your condition: whether it's primary or secondary hypothyroidism and what may/may not have caused it, or what you can do to improve your symptoms.

More discussions about hypothyroidism
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