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Alternative Names Return to topThyrotoxicosis; Overactive thyroid
Definition Return to top
Hyperthyroidism is a condition in which the thyroid gland is overactive, and makes too much thyroid hormone (called thyroxine [T4 ] and triiodothyronine [T3 ]). Hormones are substances that affect and control many important functions in the body.
Causes Return to top
The thyroid gland is located in the neck. It produces several hormones that control the way every cell in the body uses energy (metabolism). The thyroid is part of the endocrine system.
Hyperthyroidism occurs when the thyroid releases too much of its hormones over a short (acute) or long (chronic) period of time. Many diseases and conditions can cause this problem, including:
Graves disease accounts for 85% of all cases of hyperthyroidism.
Symptoms Return to top
Other symptoms that can occur with this disease:
Exams and Tests Return to top
Physical examination may reveal thyroid enlargement, goiter, or an increased heart rate. Systolic blood pressure (the first number in a blood pressure reading) may be high.
Laboratory tests that evaluate thyroid function:
This disease may also affect the results of the following tests:
Treatment Return to top
How the condition is treated depends on the cause and the severity of symptoms. Hyperthyroidism is usually treated with:
If the thyroid must be removed with radiation or surgery, you must take thyroid hormone replacement pills for the rest of your life.
Beta-blockers such as propranolol are used to treat some of the symptoms, including rapid heart rate, sweating, and anxiety until the hyperthyroidism can be controlled.
Outlook (Prognosis) Return to top
Hyperthyroidism is generally treatable and only rarely is life-threatening. Some of its causes may go away without treatment.
Hyperthyroidism caused by Graves disease usually gets worse over time. It has many complications, some of which are severe and affect quality of life.
Treatments for hypothyroidism, such as radioactive iodine, surgery, and medications to replace thyroid hormones can have complications.
Possible Complications Return to top
When to Contact a Medical Professional Return to top
Call your health care provider if you have symptoms that could be caused by too much thyroid hormone production. Go to an emergency room or call the local emergency number (such as 911), if you have:
Call your health care provider if you are being treated for hyperthyroidism and you develop symptoms of underactive thyroid, including:
Prevention Return to top
There are no known ways to prevent hyperthyroidism.
References Return to top
AACE Thyroid Task Force. American Association of Clinical Endocrinologists medical guidelines for clinical practice for the evaluation and treatment of hyperthyroidism and hypothyroidism. Endocr Pract. 2002;8(6).
Davies TF, Larsen PR. Thyrotoxicosis. In: Koronenberg HM, Shlomo M, Polonsky KS, Larsen PR, eds. Williams Textbook of Endocrinology. 11th ed. Philadelphia, Pa: Saunders Elsevier; 2008:chap 11.Update Date: 7/18/2008 Updated by: David C. Dugdale, III, MD, Professor of Medicine, Division of General Medicine, Department of Medicine, University of Washington School of Medicine; and Deborah Wexler, MD, Assistant Professor of Medicine, Harvard Medical School, Endocrinologist, Massachusetts General Hospital. Also reviewed by David Zieve, MD, MHA, Medical Director, A.D.A.M., Inc.