Hyperthyroidism Overview

Overactive thyroid makes too much thyroid hormone

Hyperthyroidism is a condition in which the thyroid gland is overactive and makes excessive amounts of thyroid hormone. The thyroid gland is an organ located in the front of your neck and releases hormones that control your metabolism (the way your body uses energy), breathing, heart rate, nervous system, weight, body temperature, and many other functions in the body. When the thyroid gland is overactive (hyperthyroidism) the body’s processes speed up and you may experience nervousness, anxiety, rapid heartbeat, hand tremor, excessive sweating, weight loss, and sleep problems, among other symptoms.

Thyroid Gland (red)

Hyperthyroidism has a number of causes and, fortunately, a number of treatment options. It is important you talk to your doctor if you think you may have symptoms of hyperthyroidism.

Symptoms
The symptoms of hyperthyroidism include the following:

  • Fatigue or muscle weakness
  • Hand tremors
  • Mood swings
  • Nervousness or anxiety
  • Rapid heartbeat
  • Heart palpitations or irregular heartbeat
  • Skin dryness
  • Trouble sleeping
  • Weight loss
  • Increased frequency of bowel movements
  • Light periods or skipping periods

Some people may develop a goiter, which is an enlarged thyroid gland that feels like a swelling in the front of your neck. See more hyperthyroidism symptoms.

Causes of Hyperthyroidism
The thyroid gland makes the hormones thyroxine (T4) and triiodothyronine (T3) that play an important role in the way your whole body functions. If your thyroid gland makes too much T4 and T3, this is defined as hyperthyroidism. 

The most common cause of hyperthyroidism is the autoimmune disorder Graves’ disease. In this disorder, the body makes an antibody (a protein produced by the body to protect against a virus or bacteria) called thyroid-stimulating immunoglobulin (TSI) that causes the thyroid gland to make too much thyroid hormone. Graves’ disease runs in families and is more commonly found in women.

Hyperthyroidism also may be caused by a toxic nodular or multinodular goiter, which are lumps or nodules in the thyroid gland that cause the thyroid to produce excessive amounts of thyroid hormones. In addition, inflammation of the thyroid gland—called thyroiditis—resulting from a virus or a problem with the immune system may temporarily cause symptoms of hyperthyroidism. Furthermore, some people who consume too much iodine (either from foods or supplements) or who take medications containing iodine (such as amiodarone) may cause the thyroid gland to overproduce thyroid hormones.

Finally, some women may develop hyperthyroidism during pregnancy or in the first year after giving birth. 

Diagnosis
Hyperthyroidism is diagnosed based on symptoms, physical exam, and blood tests to measure levels of thyroid stimulating hormone (TSH) and thyroid hormones T3 and T4. Your doctor may also decide to order either an ultrasound or a nuclear medicine scan of your thyroid to see if it has nodules, or whether it is inflamed or  overactive.

Treatment of Hyperthyroidism
Hyperthyroidism can be treated with antithyroid medications that interfere with the production of thyroid hormones (primarily methimazole; propylthiouracil is now used only for women in the first trimester of pregnancy). Another option is radioactive iodine therapy to damage the cells that make thyroid hormones. In rare cases in which women do not respond to or have side effects from these therapies, surgery to remove the thyroid (either one part of the entire gland) may be necessary. The choice of treatment will depend on the severity and underlying cause of your symptoms, your age, whether you are pregnant, other conditions you may have, and the potential side effects of the medication. 

In addition to these treatments, your doctor may also prescribe beta-blockers to block the effects of thyroid hormones on your body. For example, beta-blockers help slow down a rapid heart rate and reduce hand tremors.

View Sources
  1. American Thyroid Association. Hyperthyroidism. June 2012. Available at: http://www.thyroid.org/what-is-hyperthyroidism/. Accessed April 7, 2014.
  2. Mayo Clinic. Hyperthyroidism (overactive thyroid). November 2012. Available at: http://www.mayoclinic.org/diseases-conditions/hyperthyroidism/basics/causes/con-20020986 Accessed April 7, 2014.
  3. National Endocrine and Metabolic Diseases Information Service. Hyperthyroidism. July 2012. NIH Publication No. 12–5415. http://www.endocrine.niddk.nih.gov/pubs/Hyperthyroidism/ Accessed April 7, 2014.