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What is hypothyroidism?

Hypothyroidism is a common disorder that occurs when the thyroid gland is underactive and does not produce enough thyroid hormone. The thyroid gland is located in the front part of the neck, and it releases hormones that regulate your metabolism and how you use energy.

The lack of thyroid hormone due to hypothyroidism slows the body’s chemical processes and metabolism. This leads to symptoms such as fatigue and weight gain. Hypothyroidism, also called myxedema, hypothyroid, or underactive thyroid, is more common in women than in men. It is also more common in people older than 50 years of age.

Hypothyroidism is not curable, but it is treatable. Left untreated, hypothyroidism may lead to serious, potentially life-threatening complications, such as heart disease and rarely, myxedema coma. Seek prompt medical care if you have symptoms of hypothyroidism, such as cold hands and feet, fatigue, and weight gain. Timely diagnosis and treatment of hypothyroidism reduces the risk of serious complications.


What are the symptoms of hypothyroidism?

The types and severity of symptoms of hypothyroidism vary, and many are associated with other conditions. At the onset of the disease, the symptoms can be vague and develop or progress slowly. Symptoms may include:

  • Brittle nails
  • Cold hands and feet
  • Constipation
  • Dry skin
  • Fatigue
  • Joint pain
  • Menstrual irregularity
  • Muscle aches
  • Sensitivity to cold (cold intolerance)
  • Thinning, brittle hair
  • Weakness (loss of strength)
  • Weight gain

Later symptoms of undiagnosed or untreated hypothyroidism can include:

  • Bradycardia (slow heartbeat)
  • Depression
  • Enlargement of the tongue
  • Slowing of speech
  • Swelling of the arms or legs
  • Swelling of the hands, feet or face
  • Thickening skin
  • Thinning eyebrows

Serious symptoms that might indicate a life-threatening condition

Any of the following symptoms can indicate worsening of hypothyroidism and a serious or possibly life-threatening situation. Seek immediate medical care (call 911) if you, or someone you are with, have any of these symptoms:


What causes hypothyroidism?

Hypothyroidism can be caused by a variety of diseases and conditions. Most commonly, hypothyroidism is the result of inflammation of the thyroid gland, which can be due to:

Hashimoto’s thyroiditis, an autoimmune disease in which the body’s immune system mistakes healthy thyroid tissue as potentially dangerous to the body and attacks it. This results in inflammation of the tissue that eventually can destroy the function of the thyroid gland.

Viral infection of the thyroid gland (viral thyroiditis)

Hypothyroidism can also be caused by:

  • Birth defects, such as being born without a thyroid gland or with an abnormal thyroid gland

  • Disorders of the pituitary gland or the hypothalamus, which are glands that control the function of the thyroid gland

  • Radiation treatments of the neck

  • Treatments for hyperthyroidism

What are the risk factors for hypothyroidism?

It is generally not possible to prevent hypothyroidism, and a number of factors can put you at risk for developing it. Not all people who are at risk for hypothyroidism will develop the disease. Risk factors include:

  • Addison’s disease (chronic endocrine disorder affecting the adrenal glands)

  • Autoimmune diseases

  • Eating disorders

  • Family history of hypothyroidism

  • Female gender, especially women over 50 years old

  • Gout

  • Increasing age


How is hypothyroidism treated?

There is no cure for hypothyroidism. However, with recognition and treatment, low levels of thyroid hormone can be replaced to reach normal levels in the body. To accomplish this, most people with hypothyroidism have to take the oral thyroid hormone replacement medication called levothyroxine for the rest of their lives.

Medication therapy is monitored closely with blood tests for several months after beginning treatment to ensure you are taking the right amount of the drug. Ideal doses vary among individuals. If the dose of thyroid hormone replacement medication is too small for an individual, it will not adequately replace thyroid hormone in the body. If the dose is too high, it may result in side effects and a potentially serious condition called hyperthyroidism.

Once a safe and effective dose of thyroid hormone replacement medication has been established, it is then generally monitored yearly, or more frequently if symptoms reappear or side effects develop. It is very important not to skip or change doses of your medication without consulting with your licensed health care provider. 

Treatment of the life-threatening complication of myxedema coma may require intravenous thyroid hormone replacement medication and steroids and intensive monitoring in a critical care unit. 

What are the possible complications of a hypothyroidism?

Complications of untreated hypothyroidism can be serious and even life-threatening in some cases. You can minimize the risk of serious complications of a hypothyroidism by following the treatment plan you and your health care professional design specifically for you.

Complications of untreated hypothyroidism include:

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Medical Reviewer: William C. Lloyd III, MD, FACS
Last Review Date: 2018 Oct 25
  1. Collins RD. Differential Diagnosis in Primary Care, 5th ed. Philadelphia: Lippincott, Williams & Williams, 2012.
  2. Bope ET, Kellerman RD (Eds.) Conn’s Current Therapy. Philadelphia: Saunders, 2013.
  3. Hypothyroidism. PubMed Health. http://www.ncbi.nlm.nih.gov/pubmedhealth/PMH0001393
  4. Hypothyroidism. Medline Plus, a service of the National Library of Medicine National Institutes of Health. http://www.nlm.nih.gov/medlineplus/ency/article/000353.htm
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