The thyroid is a small, butterfly-shaped gland located in the neck, in front of the trachea, or windpipe, the tube through which air passes to the lungs. The thyroid consists of two lobes connected by a thin tissue called the isthmus. The gland produces thyroid hormones, which regulate metabolism—the conversion of food to energy.
The thyroid takes the mineral iodine—found in table salt, seafood, and dairy products—from the bloodstream and uses it to produce the thyroid hormones thyroxine (T4) and triiodothyronine (T3).
T3 helps regulate your heart rate. It also controls your metabolism—the speed with which food is digested and glucose, or sugar, is produced and used in the body. T4 plays the same role, but it’s more powerful and acts more rapidly.
The thyroid produces T4 and T3 after the pituitary gland, a small organ at the base of the brain, releases a hormone called thyroid-stimulating hormone, or TSH. When thyroid hormone levels are low, the pituitary releases more TSH. When thyroid hormone levels are high, TSH levels are suppressed.
Benign Thyroid Nodules
Thyroid nodules are small growths that develop when thyroid cells grow abnormally. About half of people have a thyroid nodule by the time they are 60. The vast majority of these nodules are noncancerous, or benign.
Benign nodules may require active surveillance, also called watchful waiting, to ensure that they do not continue to grow. Doctors make sure the nodules are not pressing on nearby structures, such as the trachea, or the esophagus, the muscular tube that carries food from the mouth to the stomach.
There are several different types of benign thyroid nodules.
Some nodules can cause the thyroid to become overactive, meaning it produces too much thyroxine. These growths are called toxic nodules. Toxic nodules can lead to a condition called hyperthyroidism, in which the body’s metabolism speeds up.
Toxic nodules are almost always benign, but they may require treatment to address hyperthyroidism. Toxic nodules may slowly become very large and press on surrounding structures in the neck or upper chest, requiring treatment.
If several nodules are found in the thyroid, the condition is called a multinodular goiter, or enlarged thyroid.
Sometimes multinodular goiters cause the thyroid to produce too much thyroxine, resulting in hyperthyroidism. These growths are called toxic multinodular goiters and may require treatment. Toxic multinodular goiters may become quite large and press on surrounding structures. This is more common in older people.
Fluid-filled spaces, or cysts, may develop in the thyroid gland. Some cysts are congenital, or present from birth.
Sometimes thyroid cysts are filled with blood, debris, and substances left behind when blood or cells break down. They may also contain calcifications, or calcium deposits. Cysts may be the result of an injury or inflammation, or may occur along with benign or cancerous growths. They may need to be drained or biopsied so that our endocrinologists can make a diagnosis.
Five to 10 percent of thyroid nodules are malignant, or cancerous, although most cause no symptoms. Rarely, they may cause neck swelling, pain, swallowing problems, shortness of breath, or changes in the sound of your voice as they grow.
There are several types of thyroid cancer. Most respond well to treatment, although some rare forms can be aggressive.
Differentiated Thyroid Cancer
This form of thyroid cancer develops from follicular cells, which bind iodine to protein, creating thyroid hormones. There are two types of differentiated thyroid cancers: papillary carcinoma and follicular carcinoma.
Papillary carcinoma accounts for about 80 percent of all thyroid cancers. It usually grows very slowly but often spreads to nearby lymph nodes—small immune system glands that help fight infection. If caught early, this type of thyroid cancer can be treated effectively. Women develop papillary carcinoma more frequently than men, and it can occur at any age.
About 10 to 15 percent of all thyroid cancers are follicular carcinomas. Follicular thyroid cancer is more common in people between the ages of 40 and 60, but it can occur at any age. This form of thyroid cancer usually does not spread to the lymph nodes. It can, however, spread to other parts of the body, such as the lungs and bones.
Caught early, follicular carcinoma can be treated effectively. A subtype called oncocytic, or Hürthle cell, cancer can become aggressive and spread to distant areas of the body, including the bones and other organs.
Medullary Thyroid Carcinoma
Medullary thyroid carcinoma develops in parafollicular cells, also called C cells. These cells produce a hormone called calcitonin, which helps control the body’s use of calcium. Sometimes, medullary thyroid carcinoma can spread to the lymph nodes, lungs, or liver before the cancer has been discovered, making it more challenging to treat. It accounts for about 5 percent of all thyroid cancers.
Medullary thyroid cancer can occur spontaneously, without apparent cause, or as part of a genetic syndrome. Genetic counselors are available at NYU Langone to discuss screening for a genetic syndrome in people with medullary thyroid carcinoma and their family members.
Anaplastic carcinoma is an extremely rare and aggressive form of thyroid cancer that rapidly invades nearby organs, such as the windpipe and esophagus. It can also spread to the lungs, bones, and brain. It can occur spontaneously, but it usually develops in people who have had longstanding thyroid cancers, in which the cells invade local structures, the bloodstream, lymph nodes, and distant organs.
Anaplastic carcinoma accounts for less than 2 percent of all thyroid cancers. It tends to occur in people older than age 65.
Like other thyroid cancers, anaplastic carcinoma also develops from follicular cells, but it is much more aggressive. Doctors at NYU Langone provide comprehensive and compassionate care for people with this form of thyroid cancer, as well as resources and support for their families.
Thyroid lymphoma accounts for about 2 percent of all thyroid cancers. It occurs most often, but still very rarely, in people with Hashimoto’s thyroiditis, in which the immune system attacks the thyroid. Symptoms such as neck swelling and pain often occur more rapidly than with other forms of thyroid cancer because the tumor grows quickly.
This type of cancer is typically non-Hodgkin lymphoma, meaning it arises from lymphocytes, white blood cells that fight infection and are found in the thyroid. Thyroid lymphoma can usually be effectively treated, like other lymphomas, with radiation therapy.
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