Hyperthyroidism is a condition in which the thyroid gland makes too much thyroid hormone. The condition is often called overactive 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 gland makes the hormones that control the way every cell in the body uses energy. This process is called metabolism.
Many diseases and conditions can cause hyperthyroidism, including:
Treatment depends on the cause and severity of symptoms. Hyperthyroidism is usually treated with one or more of the following:
Radioactive iodine to destroy the thyroid gland and stop the excess production of hormones
Surgery to remove the thyroid
If your thyroid is removed with surgery or destroyed with radioactive iodine, you must take thyroid hormone replacement pills for the rest of your life.
Medicines called beta-blockers may be prescribed to treat symptoms such as fast heart rate, sweating, and anxiety until the hyperthyroidism can be controlled.
Hyperthyroidism is treatable. 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.
Thyroid crisis (storm) is a sudden worsening of hyperthyroidism symptoms that may occur with infection or stress. Fever, decreased alertness, and abdominal pain may occur. Patients need to be treated in the hospital.
Other complications of hyperthyroidism include:
Heart problems such as fast heart rate, abnormal heart rhythm, and heart failure
Surgery-related complications, including:
Scarring of the neck
Hoarseness due to nerve damage to the voice box
Low calcium level due to damage to the parathyroid glands (located near the thyroid gland)
Hypothyroidism (underactive thyroid)
When to Contact a Medical Professional
Call your health care provider if you have symptoms of hyperthyroidism. Go to an emergency room or call the local emergency number (such as 911) if you have:
Change in consciousness
Rapid, irregular heartbeat
Call your health care provider if you are being treated for hyperthyroidism and you develop symptoms of underactive thyroid, including:
Mental and physical sluggishness
Bahn RS, Burch HB, Cooper DS, et al. Hyperthyroidism and other causes of thyrotoxicosis: Management Guidelines of the American Thyroid Association and American Association of Clinical Endocrinologists. Endocr Pract. 2011;17:457-520.
Brent Wisse, MD, Associate Professor of Medicine, Division of Metabolism, Endocrinology & Nutrition, University of Washington School of Medicine. Also reviewed by David Zieve, MD, MHA, Isla Ogilvie, PhD, and the A.D.A.M. Editorial team.