Mayo Clinic Health Manager
Get free personalized health guidance for you and your family.
Get Started
About our e-newsletters
- Free e-newsletters
- Mayo Clinic expertise
- We do not share your e-mail address
Housecall, our weekly general-interest e-newsletter, keeps you up to date on a wide variety of health topics with timely, reliable, practical information, recipes, blogs, questions and answers with Mayo Clinic experts and more. Our biweekly topic-specific e-newsletters also include blogs, questions and answers with Mayo Clinic experts, and other useful information that will help you manage your health.
Housecall Archives
Mayo Clinic Housecall
Stay up to date on the latest health information.
What you get
- Free weekly e-newsletter
- Mayo Clinic expertise
- Recipes, tools and other helpful information
- We do not share your e-mail address
Causes
By Mayo Clinic staff
Your thyroid gland consists of two lobes that resemble the wings of a butterfly. The thyroid takes up iodine from food you eat and uses it to manufacture two main hormones, thyroxine (T4) and triiodothyronine (T3). These hormones 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. Your thyroid gland also produces calcitonin, a hormone that regulates the amount of calcium in your blood.
It's not known what causes most nodules to develop, but the following factors are sometimes involved:
- A lack of iodine in your diet
- Hashimoto's disease, an autoimmune disorder that causes chronic inflammation — and underactivity (hypothyroidism) — of your thyroid gland
- A genetic defect of receptors that release thyroid-stimulating hormone (TSH)
- Radiation treatments to your head or neck in childhood
Several types of nodules can develop in your thyroid gland:
- Colloid nodule. Most thyroid nodules are colloid nodules — noncancerous (benign) overgrowths of normal thyroid tissue. You may have just one colloid nodule or many. Although these nodules may grow larger, they don't spread beyond your thyroid gland.
- Follicular adenoma. This type of nodule also is benign.
- Thyroid cyst. These fluid-filled areas of the thyroid can range in size from less than 1/3-inch (about 8 millimeters) in diameter to 1 inch (25 millimeters) or more. Many thyroid cysts are entirely filled with fluid, but some cysts, called complex cysts, also have solid components. Fluid-filled cysts are usually benign, but complex cysts are sometimes malignant.
- Inflammatory nodule. This occasionally develops as a result of chronic inflammation of your thyroid gland (thyroiditis). One rare type of thyroiditis — subacute thyroiditis — causes severe pain in the thyroid gland. Other types are painless and sometimes occur after pregnancy (postpartum thyroiditis).
- Thyroid cancer. Although the chances that a nodule is malignant are small, you're at higher risk if you have a family history of thyroid or other endocrine cancers, are younger than 30 or older than 60, are a man, or have a history of head or neck radiation. Malignant nodules are usually large and hard and may cause neck discomfort or pain.
- Multinodular goiter. "Goiter" is a term used to describe any enlargement of the thyroid gland. Several factors can lead to a goiter, including the presence of a number of thyroid nodules. This condition, called multinodular goiter, can cause a tight feeling in your throat and difficulty breathing or swallowing.
-
Hyperfunctioning thyroid nodule (toxic adenoma, toxic multinodular goiter, Plummer's disease). These nodules grow and produce thyroid hormones independent of the influence of TSH, a substance released by the pituitary gland, which normally regulates the production of your thyroid hormones.
Hyperfunctioning thyroid nodules cause high blood levels of thyroxine along with low or nonexistent levels of TSH. A genetic defect of the TSH receptors may play a role in the overactivity of these nodules.
- Thyroid nodules. American Thyroid Association. www.thyroid.org/patients/brochures/Nodules_brochure.pdf. Accessed Oct. 9, 2008.
- Ross DS. Diagnostic approach to and treatment of thyroid nodules. http://www.uptodate.com/online/content/topic.do?topicKey=thyroid/8983&selectedTitle=1~70&source=search_result. Accessed Oct. 9, 2008
- Ross DS. Overview of thyroid nodule formation. http://www.uptodate.com/online/content/topic.do?topicKey=thyroid/2323&selectedTitle=2~70&source=search_result. Accessed Oct. 9, 2008.
- Approach to the Patient With a Thyroid Nodule. The Merck Manual for Healthcare Professionals. http://www.merck.com/mmpe/sec12/ch152/ch152b.html?qt=thyroid%20nodules&alt=sh. Accessed Oct. 9, 2008.
- Ridgway EC. Medical treatment of benign thyroid nodules: Have we defined a benefit? Annals of Internal Medicine. 1998;128:403
- Lee GA et al. Disorders of the Thyroid Gland. In: Lalwani AK. Current Diagnosis & Treatment in Otolaryngology — Head & Neck Surgery. 2nd ed. New York, N.Y.: The McGraw-Hill Companies; 2008. http://www.accessmedicine.com/content.aspx?aID=2829111. Accessed Dec. 16, 2008.
- Clark OH. Thyroid & Parathyroid: Evaluation of Thyroid Nodules & Goiter. In: Doherty GM et al. Current Surgical Diagnosis & Treatment. 12th ed. Ann Arbor, Mich.: The McGraw-Hill Companies; 2006. http://www.accessmedicine.com/content.aspx?aID=2061372. Accessed Dec. 16, 2008.
