Hypothyroidism is a condition in which the thyroid gland does not make enough thyroid hormone.
The thyroid gland is located in the front of the neck just below the voice box (larynx). It releases hormones that control metabolism.
Hypothyroidism, or underactive thyroid, 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 left untreated:
A physical examination may reveal a smaller-than-normal thyroid gland, although sometimes the gland is normal size or even enlarged (goiter). The examination may also reveal:
Lab tests to determine thyroid function include:
Other tests that may be done:
The purpose of treatment is to replace the thyroid hormone that is lacking. Levothyroxine is the most commonly used medication.
When starting your medication, your doctor may check your hormone levels every 2 - 3 months. After that, your thyroid hormone levels should be monitored at least every year.
Important things to remember when you are taking thyroid hormone:
While you are taking thyroid replacement therapy, tell your doctor if you have any symptoms that suggest your dose is too high, such as:
Myxedema coma is a medical emergency that occurs when the body's level of thyroid hormones becomes very low. It is treated with intravenous thyroid hormone replacement and steroid medications. Some patients may need supportive therapy (oxygen, breathing assistance, fluid replacement) and intensive-care nursing.
In most cases, thyroid levels return to normal with proper treatment. However, you must take thyroid hormone replacement for the rest of your life.
Myxedema coma can result in death.
Myxedema coma, the most severe form of hypothyroidism, is rare. It may be caused by an infection, illness, exposure to cold, or certain medications in people with untreated hypothyroidism.
Symptoms and signs of myxedema coma include:
Other complications are:
People with untreated hypothyroidism are at increased risk for:
People treated with too much thyroid hormone are at risk for angina or heart attack, as well as osteoporosis (thinning of the bones).
Call your health care provider if you have symptoms of hypothyroidism (or myxedema).
If you are being treated for hypothyroidism, call your doctor if:
There is no prevention for hypothyroidism.
Screening tests in newborns can detect hypothyroidism that is present from birth (congenital hypothyroidism).
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: Saunders Elsevier; 2011:chap 13.
Kim M, Ladenson P. Thyroid. In: Goldman L, Schafer AI, eds. Cecil Medicine. 24th ed. Philadelphia, Pa: Saunders Elsevier; 2011:chap 233.
Updated by: David C. Dugdale, III, MD, Professor of Medicine, Division of General Medicine, Department of Medicine, University of Washington School of Medicine. Also reviewed by Shehzad Topiwala, MD, Chief Consultant Endocrinologist, Premier Medical Associates, The Villages, FL. Review provided by VeriMed Healthcare Network. Also reviewed by David Zieve, MD, MHA, Medical Director, A.D.A.M. Health Solutions, Ebix, Inc.
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