Hypothyroidism is a condition in which the thyroid gland does not make enough thyroid hormone. This condition is often called underactive thyroid.
The thyroid gland is an important organ of the endocrine system. It is located at the front of the neck, just above where your collarbones meet. The thyroid makes hormones that control the way every cell in the body uses energy. This process is called metabolism.
Hypothyroidism is more common in women and people over age 50.
The most common cause of hypothyroidism is thyroiditis. Swelling and inflammation damage the thyroid gland's cells.
Causes of this problem include:
Other causes of hypothyroidism include:
Late symptoms, if untreated:
The health care provider will do a physical exam and find that your thyroid gland is enlarged. Sometimes, the gland is normal size or smaller-than-normal. The exam may also reveal:
You may also have tests to check:
Treatment is aimed at replacing the thyroid hormone you are lacking.
Levothyroxine is the most commonly used medicine:
When starting you on your medicine, your doctor may check your hormone levels every 2 to 3 months. After that, your thyroid hormone levels should be monitored at least once every year.
When you are taking thyroid medicine, be aware of the following:
While you are taking thyroid replacement therapy, tell your doctor if you have any symptoms that suggest your dose is too high, such as:
In most cases, thyroid hormone levels become normal with proper treatment. You will likely take a thyroid hormone medicine for the rest of your life.
Myxedema coma, the most severe form of hypothyroidism, is rare. It occurs when thyroid hormone levels get very low. It can be caused by an infection, illness, exposure to cold, or certain medicines in people with untreated hypothyroidism.
Myxedema coma is a medical emergency that must be treated in the hospital. Some patients may need oxygen, breathing assistance (ventilator), fluid replacement, and intensive-care nursing.
Symptoms and signs of myxedema coma include:
People with untreated hypothyroidism are at increased risk of:
Call your health care provider if you have symptoms of hypothyroidism.
If you are being treated for hypothyroidism, call your doctor if:
Myxedema; Adult hypothyroidism
Brent GA, Davies TF. Hypothyroidism and thyroiditis. In: Melmed S, Polonsky KS, Larsen PR, Kronenberg HM, et al. Williams Textbook of Endocrinology. 12th ed. Philadelphia, PA: Elsevier Saunders; 2011:chap 13.
Garber JR, Cobin RH, Gharib H, et al. Clinical practice guidelines for hypothyroidism in adults: cosponsored by the American Association of Clinical Endocrinologists and the American Thyroid Association. Thyroid. 22;12:1200-1235.
Kim M, Ladenson P. Thyroid. In: Goldman L, Schafer AI, eds. Goldman's Cecil Medicine. 24th ed. Philadelphia, PA: Elsevier Saunders; 2011:chap 233.
Updated by: Brent Wisse, MD, Associate Professor of Medicine, Division of Metabolism, Endocrinology & Nutrition, University of Washington School of Medicine, Seattle, WA. Also reviewed by David Zieve, MD, MHA, Isla Ogilvie, PhD, and the A.D.A.M. Editorial team.
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