Hyperthyroidism is a condition in which the body has too much thyroid hormone in the blood. Thyroid hormone is made by the thyroid gland, a butterfly-shaped gland in the front of the neck. It produces the hormones thyroxine (T4) and triiodothyronine (T3), which control metabolism. This affects:

    
  • How many calories you burn
  • How warm you feel
  • How much you weigh
  • How the body handles many other vital functions of the cardiovascular, gastrointestinal, and nervous systems—Thyroid hormones directly affect the heart. If you have too much thyroid hormones in your blood, it will cause your heart to beat harder and faster.
  • The Thyroid Gland

    Copyright © Nucleus Medical Media, Inc.

    The most common form of hyperthyroidism is Graves disease. Graves disease occurs when your own immune system produces antibodies that stimulate the thyroid gland to overproduce thyroid hormone. Hyperthyroidism can be the result of other conditions, such as:

        
  • Inflammation of the thyroid (generally goes away on its own over weeks to months)
  • Formation of nodule on the thyroid (the nodule works independently from the rest of the thyroid)
  • Self-administered dose of too much thyroid
  • Ingesting too much iodine (rarely)
  • Substances secreted by tumors of the thyroid gland, testes, or ovaries (which stimulate the thyroid gland)
  • Treatment of hyperthyroidism can lead to the opposite condition, hypothyroidism. This is a condition in which the thyroid gland produces too little thyroid hormone. It is easier to treat hypothyroidism long-term than hyperthyroidism. Treatment of hypothyroidism involves taking a pill of thyroid hormone.

    It is estimated that 20 million Americans have thyroid disorders. These disorders affect more women than men—one in eight women will develop a thyroid disorder in her lifetime. Hyperthyroidism can occur at any age, but it is more common in people aged 60 and older.