The thyroid gland is the gland that makes and stores hormones that help regulate the heart rate, blood pressure, body temperature, and metabolism. Thyroid hormones are essential for the function of every cell in the body. They help regulate growth and the rate of chemical reactions in the body. Thyroid hormones also help children grow and develop. The thyroid gland is located in the lower part of the neck, below the Adam’s apple, wrapped around the trachea. It has the shape of a butterfly with two lobes attached to one another by a middle part called the isthmus.
The thyroid uses iodine, a mineral found in some foods and in iodized salt, to make its hormones. The two most important thyroid hormones are thyroxine (T4) and triiodothyronine (T3). The thyroid gland also makes the hormone calcitonin, which is involved in calcium metabolism and stimulating bone cells to add calcium to bone. Thyroid caner is a disease in which the cells of the thyroid gland become abnormal, grow uncontrollably and form a mass of cells called a tumor. Some tumors grow and enlarge only at the site where they began. These types of tumors are referred to as benign tumors.
Other tumors not only enlarge locally, but they also have the potential to invade and destroy the normal tissues around them and to spread to other regions of the body. These types of tumors are called malignant tumors or cancer. () Malignant tumors of the thyroid gland tend to develop gradually and remain localized. The tumors usually appear as nodules or lumps of tissue growing on or inside the gland itself. Almost 95% of these lumps or nodules are non-cancerous (benign), and are usually caused by thyroid conditions such as goiters (Shin 422).
The American Cancer Society estimates that there will be about 23,600 new cases of thyroid cancer in the U. S. in 2004 (Thackery 1057). Women are three times more likely to develop thyroid cancer than men. Although the disease also affects younger people, most people who develop thyroid cancer are over 50 years of age. Caucasians are affected more often than African-Americans (Rubin 88). There are four main types of thyroid cancers: papillary, follicular, medullary, and anaplastic. These tumors are identified by the type of cells seen under the microscope.
Papillary thyroid tumors occur most often. This type of thyroid cancer develops on one or both sides of the gland and remains confined for several years and accounts for 60% – 80% of all thyroid cancers (Thackery 1057). Follicular tumors, on the other hand, grow only on one side of the gland. These tumors develop in the hormone-producing cells and account for 30% – 50% of all thyroid cancers (Thackery 1057). Medullary thyroid tumors account for 5% – 7% of all thyroid cancers, and are usually uncommon. Like papillary tumors, they grow on one or both sides of the gland.
Anaplastic tumors, though extremely rare, develop on either side of the thyroid gland and spread rapidly to other parts of the body. It account for only 2% of all thyroid cancers but is the fastest growing, and most aggressive thyroid cancer type (Thackery 1057). The aggressiveness of each type of thyroid cancer is different. There are four main stages in each of the types of thyroid cancer except for anaplastic cancer (Rubin 91). In the stage I of papillary and follicular thyroid cancer, the cancer is located only in the thyroid and may be found in one or both of the lobes.
In stage II if the patients are younger than 45 years of age, the cancer has spread beyond the thyroid. But if the patient is older than 45 years of age, the cancer is only in the thyroid and is larger than 1 centimeter. In stage III, the cancer is usually found in patients older than 45 years of age and has spread outside of the thyroid or has spread to the lymph nodes but not outside of the neck. In stage IV, the cancer is again usually found in patients over the age of 45. It most likely has spread to other parts of the body such as the lungs or bones (Thackery 1058).
Medullary thyroid cancer is quite uncommon. In stage I, the is located in one or both of the thyroid glands and is about 1 centimeter in size, but throughout the last three stages of medullary thyroid cancer, the tumor grows by 1-4 centimeters and continuously spreads to other parts of the body (Shin 93). There is no staging system for anaplastic cancer of the thyroid. This cancer is located in either of the lobes and spreads faster than any of the other types (Thackery 1058). The exact cause of thyroid cancer is not known but some risk factors have been identified.
From the early 1950’s to the late 1960’s, thousands of children received radiation to treat acne and to reduce infection of the tonsils, adenoids and lymph nodes (Shin 419). It has been proven that radiation is a risk factor for thyroid cancer. Another risk factor is diets that are low in iodine. In parts of the world that have low iodine diets papillary and follicular cancers occur more frequently (Ruben 86). Other risks factors for thyroid cancer include patients with a family history of thyroid cancer. Approximately 7% of thyroid cancer is caused by alteration of a gene called the RET oncogene, which can be inherited (Thackery 1057).
Symptoms are rare, and the lump is not usually painful. The lump that can be felt in the neck is the most frequent sign of thyroid cancer. Swelling of the lymph nodes are another symptom. Such symptoms could possibly be roughness or a slight change in the voice due to pressure from the tumor on the nerve connected to the voice box or, difficultly in swallowing or breathing due to a tumor obstructing the esophagus or trachea (Longe 3306). Most cases of thyroid cancer are found during a routine physical examination. If the gland appears to be enlarged, the physician may order further tests to diagnose or rule out cancer.
These tests include: a CT scan or ultrasonography. The ultrasound uses high-frequency sound waves that are emitted and received by a transducer that is passed over the neck region. The sound waves penetrate the body, and by electronic readings, the sound waves are arranged on a computer screen into a picture image of the thyroid gland and any tumors (Thackery 1058). Another test used is the thyroid scan. A patient is given radioactive iodine to drink. After the iodine has been absorbed by the thyroid, the patient must lie on his or her back with the neck region positioned under a scanner.
The information received by the scanner is then sent to a computer that displays a 2-dimensional image of the thyroid used to identify areas in the thyroid that do not absorb iodine normally (Surks 165). The most accurate diagnostic tool for thyroid cancer is biopsy. The test is done in a hospital operating room under a general anesthesia. A sedative is usually given by an injection about one hour before the procedure. A small incision is made in the neck, and either side of the thyroid or the entire lump is removed. The sample is sent to a laboratory to be examined.
If thyroid cancer is detected, the thyroid is removed (Shin 420). There are basically four different types of treatments used on patients with cancer of the thyroid: surgery, radiation therapy, hormone therapy, and chemotherapy (Longe 3307). Each treatment is widely used in fight against thyroid cancer, but not all have the same results. Surgery is the most common treatment for thyroid cancer. Surgical removal is the usual treatment if the cancer has not spread to other parts of the body. A physician can remove the cancer by using one or several operations.
A lobectomy removes only the side of the thyroid where the cancer is found. A near-total thyroidectomy removes the entire thyroid except for a small portion. A total thyroidectomy removes the entire thyroid, and a lymph node dissection removes lymph nodes in the neck that contain cancer (Surks 161). Another treatment is radiation therapy, which uses high-energy x-rays to kill cancer cells and shrink tumors. Radiation for thyroid cancer may come from a machine outside of the body (external radiation therapy) or from drinking a liquid that contains radioactive iodine.
Radioactive iodine may be used in addition to surgery in papillary and follicular thyroid cancers. Because the thyroid absorbs the iodine, the radioactive iodine collects in any thyroid tissue remaining in the body and kills the cancer cells (Shin 415). Hormone therapy is another type of treatment which uses hormones to stop cancer cells from growing. In treating thyroid cancer, hormones can be used to stop the thyroid gland from making other hormones that might make cancer cells grow. The hormones are usually ingested orally in the form of a pill.
Hormone treatment is aimed at killing or slowing the growth of cancer cells throughout the body (Thackery 1059). For advanced thyroid cancers for which surgery was not an option or the other treatment didn’t work, chemotherapy may be tried. Chemotherapy uses drugs to kill cancer cells. Chemotherapy may be taken by a pill, or it may be put into the body by a needle in the vein or muscle. Chemotherapy is called a systemic treatment because the drug enters the blood stream, travels through the body, and can kill the cancer cells outside of the thyroid (Longe 3307).
After thyroid surgery, some patients experience: difficulty swallowing, voice change, and damage to the parathyroid gland. If all four parathyroid glands are injured or damaged, patients may need to take calcium supplements for a few weeks (Surks 163-164). Following radioiodine treatment, many patients experience neck tenderness, nausea, stomach irritation and dry mouth. There are also many side effects for chemotherapy such as anemia, nausea, hair loss, and inflammation of the oral mucosa (Thackery 1060). Most thyroid cancers are very curable. The most common types of thyroid cancer papillary and follicular are the most curable.
In both papillary and follicular cancer, more than 90% of patients will live for 15 years or longer after the diagnosis of thyroid cancer (Longe 3307). Medullary cancer of the thyroid is significantly less common, but has a worse prognosis. Medullary cancers tend to spread to large numbers of lymph nodes very early on, and therefore require a much more aggressive operation than does the more localized cancers such as papillary and follicular. Still 85% of patients will live for at least 10 years after surgery (Longe 3307). The least common type of thyroid cancer is anaplastic which has a very poor prognosis.
It tends to be found after it has spread and is not cured in most cases. Only 3% – 17% of patients will survive for five years (Thackery 1059). Most people with thyroid cancer have no known risk factors. Therefore it may not be possible to prevent it. However, inherited cases of medullary thyroid cancer can be prevented if radiation to the neck is avoided (Longe 3308). If a family member has had the disease, the rest of the family can be testes and treated early. The National Cancer Institute recommends an examination for anyone who has received radiation to the head and neck area during childhood at intervals of one or two years.
It is also recommended that the neck and the thyroid should be carefully examined for any lumps or enlargement of the nearby lymph nodes.
Work Cited Longe, Jacqueline L. “Thyroid Cancer. ” The Gale Encyclopedia of Medicine. 2nd ed. 2001. Rubin, Alan L. Thyroid for Dummies. New York, NY: Hungry Minds, 2001. Shin, Linda M. Endocrine and Metabolic Disorders Sourcebook. Detroit, MI: Omnigraphics, 1998 Surks, Martin I. The Thyroid Book. Yonkers, NY: Consumer Reports Books, 1993 Thackery, Ellen. “Thyroid Cancer. “