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Causes
By Mayo Clinic staff
Your thyroid gland is part of your endocrine system, which produces hormones that coordinate many of your body's activities, from digestion to metabolism to reproduction. Your thyroid gland produces two main hormones, thyroxine (T-4) and triiodothyronine (T-3). They maintain the rate at which your body uses fats and carbohydrates, help control your body temperature, influence your heart rate and help regulate the production of protein.
The rate at which thyroxine and triiodothyronine are released is controlled by your pituitary gland and your hypothalamus — an area at the base of your brain that acts as a thermostat for your whole system. The hypothalamus signals your pituitary gland to make a hormone called thyroid-stimulating hormone (TSH). Your pituitary gland then releases TSH — the amount depends on how much thyroxine and triiodothyronine are detected in your blood. Finally, your thyroid gland regulates its production of hormones based on the amount of TSH it receives. Although this process usually works well, the thyroid sometimes fails to produce enough hormones.
Your immune system's role
Normally, your immune system uses naturally occurring proteins (antibodies) and white blood cells (lymphocytes) to help protect against viruses, bacteria and foreign substances (antigens) that invade your body. Hashimoto's disease is an autoimmune disorder in which your immune system creates antibodies that damage your thyroid gland. The disease causes inflammation of your thyroid gland (thyroiditis), which may impair the ability of your thyroid to produce hormones, leading to an underactive thyroid gland (hypothyroidism). Then, your pituitary gland attempts to stimulate your thyroid gland to produce more thyroid hormones, thus causing your thyroid gland to enlarge (goiter).
Doctors don't know what causes your immune system to attack your thyroid gland. Some scientists think a virus or bacterium might trigger the response, while others believe a genetic flaw may be involved. A combination of factors, including heredity, sex and age, may determine your likelihood of developing the disorder. Hashimoto's disease is most common in middle-aged women and tends to run in families.
- Hashimoto's Disease: What it is and how it's treated. American Academy of Family Physicians. http://familydoctor.org/online/famdocen/home/common/hormone/548.html. Accessed December 9, 2008.
- Hennessey J, et al, eds. Hashimoto's disease. The Hormone Foundation. http://www.hormone.org/Resources/Thyroid/loader.cfm?csModule=security/getfile&pageid=1113. Accessed December 9, 2008.
- Brent GA, et al. Hypothyroidism and thyroiditis. In: Kronenberg HM, et al, eds. Williams Textbook of Endocrinology. 11th ed. St. Louis, Mo.: W.B. Saunders; 2008:387.
- Davies, TF. Pathogenesis of Hashimoto's thyroiditis (chronic autoimmune thyroiditis). http://www.uptodate.com/home/index.html. Accessed December 9, 2008.
- Frequently asked questions: Hashimoto's thyroiditis. US Department of Health & Human Services. http://www.4woman.gov/faq/hashimoto-thyroiditis.cfm. Accessed December 9, 2008.
- Hashimoto's thyroiditis. The Merck Manuals Online Medical Library: The Merck Manual for Healthcare Professionals. http://www.merck.com/mmpe/sec12/ch152/ch152d.html. Accessed December 9, 2008.
- Ross DS. Treatment of hypothyroidism. http://www.uptodate.com/home/index.html. Accessed December 9, 2008.
