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What is hyperthyroidism?

Hyperthyroidism is a disease in which an overactive thyroid gland produces too much thyroid hormone. The thyroid gland is located in the front of the neck and produces a hormone critical to normal metabolism.

When the thyroid gland produces too much thyroid hormone, it leads to overstimulation of the body’s metabolism. Typical symptoms include nervousness, anxiety, weight loss, and hypertension.

Hyperthyroidism can be caused by a variety of factors, including an autoimmune response of the body or an abnormal growth on the thyroid gland. A condition called Graves’ disease is the most common cause of hyperthyroidism. Other causes include thyroid nodules, iodine-induced hyperthyroidism, and excessive levels of thyroid stimulating hormone from the pituitary gland. Hyperthyroidism is more common in women than in men.

Prompt diagnosis and treatment of hyperthyroidism can lead to a good prognosis or a cure in some cases. With regular medical care and compliance with treatment plans, many people with the disease live active, normal lives.

Hyperthyroidism can lead to serious, potentially life-threatening symptoms and complications, such as cardiac arrhythmias and heart failure. Seek immediate medical care (call 911) if you, or someone you are with, have symptoms such as chest pain, palpitations, or shortness of breath.

What are the symptoms of hyperthyroidism?

Symptoms of hyperthyroidism are caused by overstimulation of metabolism due to an overproduction of thyroid hormone. Symptoms can include:

  • Anxiety and nervousness

  • Diarrhea

  • Difficulty sleeping

  • Extremely smooth skin and changes in the nails

  • Eye symptoms, such as bulging eyes, eye puffiness, light sensitivity, and an intense stare

  • Feeling overenergized

  • Goiter (swelling of the thyroid gland in the front of the neck)

  • Increased appetite

  • Increased sensitivity to heat

  • Muscle weakness and fatigue

  • Shaky hands or tremors

  • Sweating

  • Unexpected weight loss

Serious symptoms that might indicate a life-threatening condition

Hyperthyroidism can lead to serious and life-threatening complications, such as angina, hypertension and heart failure. Seek immediate medical care (call 911) if you, or someone you are with, have any of the following symptoms:

What causes hyperthyroidism?

Hyperthyroidism occurs when the thyroid gland is overactive and produces too much thyroid hormone, which is important for normal metabolism. A variety of conditions can stimulate the thyroid gland to make too much thyroid hormone.

Causes of hyperthyroidism include:

  • Autoimmune thyroid disease (Graves’ disease), in which the thyroid gland is attacked by the body’s own immune system. This is the most common cause of hyperthyroidism.

  • Excess levels of thyroid stimulating hormone from the pituitary gland

  • Iodine-induced hyperthyroidism 

  • Thyroid nodule, a noncancerous cyst that grows on the thyroid gland and produces additional thyroid hormone

  • Thyroiditis, which is an inflammation of the thyroid gland due to a viral infection

What are the risk factors for hyperthyroidism?

Women are more likely than men to develop hyperthyroidism, and a number of other factors increase the risk of developing the disease. Not all people who are at risk for hyperthyroidism will develop the condition. Risk factors include:

  • Certain common viral infections

  • Drug treatments, such as certain cancer and AIDS treatments 

  • Excessive thyroid hormone for treatment of hypothyroidism

  • Family history of Grave’s disease

  • History of autoimmune diseases

  • Recent pregnancy

  • Taking iodine supplements or iodine exposure

  • Thyroid trauma or injury

How is hyperthyroidism treated?

Hyperthyroidism cannot be prevented. However, with prompt diagnosis and treatment, high levels of thyroid hormone can be returned to normal levels in the body. With regular medical care and monitoring of hyperthyroidism, many people live active, normal lives.

Treatment of hyperthyroidism includes:

  • Beta blockers, which can minimize some symptoms, such as rapid heart rate and anxiety

  • Antithyroid medications, which decrease overproduction of thyroid hormones. In some cases, antithyroid medications may cure hyperthyroidism.

  • Surgery to remove the overactive thyroid gland may be performed in some cases of hyperthyroidism. This can cure the disorder.

  • Swallowing of radioactive iodine, which reduces overactivity and overproduction of thyroid hormone

  • Testing levels of thyroid hormone in the blood and lowering the dosage of thyroid hormone used to treat hypothyroidism

What are the possible complications of hyperthyroidism?

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

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Medical Reviewer: William C. Lloyd III, MD, FACS
Last Review Date: 2020 Nov 22
  1. Bope ET, Kellerman RD (Eds.) Conn’s Current Therapy. Philadelphia: Saunders, 2013.
  2. Brent GA. Clinical practice. Graves' disease. N Engl J Med 2008; 358:2594.
  3. Hyperthyroidism. Medline Plus, a service of the National Library of Medicine National Institutes of Health. http://www.ncbi.nlm.nih.gov/pubmedhealth/PMH0001396
  4. Hyperthyroidism. National Endocrine and Metabolic Diseases Information Service, a service of the National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health. http://endocrine.niddk.nih.gov/pubs/Hyperthyroidism/
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