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Thyroid Guide


Thyroid cancer

Thyroid cancer

General Overview
Thyroid cancer is a cancerous growth, which begins in the thyroid gland. The thyroid is a small butterfly-shaped gland, which rests in the lower neck. Its main function is to control your body's growth and metabolism. To control metabolism, your thyroid gland produces hormones (thyroxine [T4] and triiodothyronine [T3]). A properly functioning thyroid will produce the right amount of hormones required to keep your body functioning normally. The most common types of thyroid cancer can often be completely removed with surgery. The prognosis is often excellent for thyroid cancer. But the important first step is to know the symptoms of thyroid cancer and see your doctor.
The level of thyroid hormones in the blood is controlled by your pituitary gland. Thyroid cancer is the most frequently occurring endocrine cancer, and it accounts for approximately 0.5 to 10 cases per 100,000 populations. Even though the overall frequency of papillary cancer is higher in regions with iodine deficiency, follicular cancer is more commonly seen. In India, thyroid cancer is prevalent among women in the coastal districts of Kerala, Karnataka, and Goa.
Introduction
What is thyroid cancer? Are there different types of thyroid cancer?
Cells are the basic building blocks of life that make up tissues, and tissues make up the organs of the body. All cancers begin in cells — the body's basic units of life. Under normal circumstances, cells grow and divide to form new cells, as the body needs them. When cells grow old and die, new cells take their place. However, sometimes this orderly process goes wrong. New cells form, when the body does not need them, and old cells do not die, when they should. These extra cells can form a mass of tissue called a growth or tumor.
A cancer, which forms in the thyroid gland, is called thyroid cancer. It can occur, if you have had any exposure to radiation or it could be due to genetic causes. Thyroid cancer is the most frequently occurring endocrine cancer, and it accounts for approximately 0.5 to 10 cases per 100,000 population. The thyroid cancer is divided into four main types depending on how the cancer cells look when viewed under the microscope. They are mentioned below.
  • Papillary thyroid cancer. This is the commonest of thyroid cancers. Nearly 8 out of the 10 thyroid cancers belong to this group. It usually develops in one lobe of the thyroid gland, and sometimes, both the lobes are affected. In spite of being a very slow growing cancer, it often spreads to the lymph nodes of the neck. It can be cured completely, if diagnosed early, and rarely, it leads to death.
  • Follicular thyroid cancer. This type of cancer accounts for about 1 out of 10 thyroid cancers. It is more common in countries, where there is a deficiency of iodine in the diet. It is less common than papillary cancer. It does not spread to the lymph nodes, but can spread to other parts of your body like the lungs and bones. You have a good chance of getting completely cured, though it is not as good as papillary cancer.
  • Medullary thyroid cancer. About 5% of all thyroid cancers belong to this group. In some cases, this cancer has already spread to lymph nodes, liver, or lungs, when first detected. The outcome of this type of cancer is not as good as those of papillary and follicular types.
  • Anaplastic thyroid cancer. This cancer makes up for 2% of all thyroid cancers. It grows very fast and spreads very fast. Treating this type is very difficult.
Signs and Symptoms
How do I know that I have thyroid cancer?
The symptoms depend on the stage of the cancer and when it is diagnosed. If your thyroid cancer is in the early stages, you will not have any symptoms. The symptoms of thyroid cancer include:
  • A swelling or lump in front of your neck.
  • Hoarseness or changes in your voice.
  • Difficulty in swallowing
  • Trouble in breathing.
  • Persistent pain in your neck or throat.
Causes
What are the causes of thyroid cancer?
The cause of thyroid cancer is not known. However, you may develop thyroid cancer due to the following.
  • Exposure to radiation. Radiation to the head and neck area even years ago contributes to the development of cancer at a later date.
  • Genetic causes. If you have a change in the gene named RET, which is passed from the parent to child, then you may develop medullary thyroid cancer either alone or along with other cancers as in multiple endocrine neoplasia (MEN) syndrome.
Risk Factors
Find out if you are at risk of developing thyroid cancer
Your risk of developing thyroid cancer increases, if you have any of the following factors.
  • Radiation. Exposure to high level of radiation as in treatment with X-rays or radioactive fallout as in atomic weapon testing increases your risk of developing thyroid cancer.
  • Inherited conditions. If you have a family history of goiter (enlargement of thyroid gland) or familial polyposis (numerous growth on the inner side of the large bowel), your risk of developing papillary cancer is high.
  • Family history. A change in the gene named RET increases your risk of developing medullary thyroid cancer either alone or along with other cancers such as in MEN syndrome.
  • Personal history. Your risk is higher, if you have had a goiter or benign nodules of the thyroid.
  • Sex. You are at increased risk of developing thyroid cancer, if you are a female, and your risk is three-fold higher than male.
  • Age. Your risk is more, if you are more than 45 years old, and your risk of developing anaplastic cancer is higher, if you are more than 60 years.
  • Race. If you are an Asian, you are at greater risk of developing thyroid cancer.
  • Iodine. Your risk of having follicular thyroid cancer increases, if your diet contains very little iodine, and your risk of developing papillary thyroid cancer increases, if your diet contains excess of iodine.
Diagnosis and Screening
How will my doctor diagnose thyroid cancer?
Your doctor will diagnose thyroid cancer based on your symptoms, history, and physical examination. He may also advise you to undertake certain tests to confirm the diagnosis.
History:
If your symptoms indicate that you may be having thyroid cancer, your doctor will question you regarding your personal and family medical history, and conduct a physical examination.
Physical examination:
Your doctor will check your thyroid for any enlargement or lumps. He will also examine your neck to detect any swelling or enlargement of the lymph nodes that are located nearby.
Blood tests:
Thyroid-stimulating hormone (TSH) test: Thyroid-stimulating hormone is a hormone produced by the pituitary gland, which regulates the production and release of the hormones T4 and T3 from the thyroid gland. During this test, your blood is collected from a vein, usually from the inside of your elbow or the back of your hand. As some drugs can alter the results, your doctor may advise you to stop them before the test. Your normal TSH level will range between 0.4 mIU/L to 4.0 mIU/L. If you are undergoing treatment for any thyroid disorder, then your TSH level should lie in the range of 0.5 mIU/L and 3.0 mIU/L. A marked increase or decrease in the level of TSH will mean that your thyroid is not working properly.
Calcitonin test: This test is usually done to diagnose medullary thyroid cancer, evaluate the efficiency of the treatment, and monitor for recurrences. In this test, initially a blood sample will be taken. Following this, you will be given an intravenous injection of either calcium or pentagastrin. This is done for stimulating the production of calcitonin (a hormone, which lowers the calcium level). Many more samples of blood are collected over the next few minutes for determining the effect of the stimulation. Significantly, elevated level of calcitonin is an indicator of medullary thyroid cancer.
Imaging:
Ultrasound of the thyroid: This is an imaging test, which uses high-frequency sound waves for detecting any abnormal growth in the thyroid. This test helps to detect thyroid nodules that cannot be felt, as they are very small. The nodules that are fluid-filled are not cancerous, while those that are solid might be due to cancer.
Thyroid scan: This is another imaging test. For doing this test, you will be asked to swallow a small quantity of radioactive substance. This substance travels throughout your blood stream. Your thyroid cells take up this substance and thereby become visible on the scan. Nodules that take up more amount of the substance than the surrounding thyroid tissue are called hot nodules. Usually, such nodules are not cancerous. Nodules that take up less amount of substance than the surrounding thyroid tissue are called cold nodules, and they might be due to cancer.
Procedure:
Fine needle aspiration biopsy: In this, your doctor removes a small sample of your thyroid tissue using a fine needle. The site for taking biopsy (test in which a small bit of tissue is removed and examined under a microscope) is determined with the help of an ultrasound device. This sample is later examined under the microscope for detecting any abnormality.
Surgical biopsy: If a diagnosis cannot be reached after doing a fine needle aspiration biopsy, your doctor will remove the whole nodule in an operation. If there is a suspicion of follicular thyroid cancer, surgical biopsy is required for making the diagnosis.
Treatment
How is thyroid cancer treated?
The treatment of thyroid cancer is usually started within a few weeks after making the diagnosis. The thyroid cancer can be in different stages depending on the rate of spread of the cancer. The choice of treatment also varies depending on the type of cancer you have, size of the nodule, your age, and also whether your cancer has already spread. The treatment options include the following.
Surgery:
Majority of the people need thyroid surgery for thyroid cancer. There are two different types of surgery depending on the type and stage of your cancer, your age, and size of the nodule. They are mentioned below.
Total thyroidectomy: This surgery may be used irrespective of the type of cancer you have. In this, an incision (cut) is made in the neck through which the entire thyroid tissue is removed. If it is not possible to remove the entire thyroid tissue, remaining thyroid tissue may be destroyed using radioactive iodine later. If the cancer has already spread to the neck, your surgeon will remove the surrounding tissues and the lymph nodes. If it has spread beyond the neck, radioactive iodine therapy, surgery, or external radiation therapy may be used to treat these sites.
Lobectomy: This surgery is usually done, if you have papillary or follicular thyroid cancer. It involves removing only a part of the thyroid gland.
Thyroid hormone treatment:
Following thyroid surgery (removing a part or the entire thyroid gland), you will have to take hormone replacement therapy for the rest of your life. This hormone helps in slowing down the growth of the thyroid cancer cells that remain in the body after the surgery.
Radioactive iodine therapy:
Your doctor will advise radioactive iodine (I-131) therapy, if you have papillary or follicular thyroid cancer. It destroys the thyroid cancer cells and the cancer cells that persist in your body after surgery. For this treatment, I-131 will be given to you either in the form of liquid or as a capsule.
External radiation therapy:
External radiation therapy is the treatment given for all types of cancer that do not respond to surgery or I-131 therapy. It is also used for treating recurrence of cancer or for treating bone pain once the cancer has spread. This therapy uses high-energy rays for killing the cancer cells.
Chemotherapy:
Your doctor will choose this treatment, if you have anaplastic thyroid cancer. This treatment may sometimes be given for relieving the symptoms of medullary or other thyroid cancers. In this treatment, drugs are injected into your vein to kill the cancer cells.
Periodically, your thyroid function level will be checked. You will be examined at regular intervals of 6 to 12 months to rule out any recurrence. The single best test, which can be done for detecting recurrence, is the measurement of serum thyroglobulin (a protein, which is stored in your thyroid gland). You doctor may also advise ultrasound test and chest X-rays to determine if the cancer persists or has been cured.
Self Care and Lifestyle Changes
Making a few changes in your lifestyle will help to strengthen your body to withstand the treatment, improve your immune system to fight against cancer, improve your emotional outlook, and also to avoid medical problems that can complicate your life. The changes that you can make include:
  • Quitting smoking.
  • Avoiding crowded places, especially during the cold and flu seasons.
  • Getting yourself immunized against flu and pneumonia.
  • Washing your hands more often and thoroughly.
  • Eating a healthy diet.
  • Undertaking a reasonable level of exercise.
  • Taking rest, when you feel tired.
  • Calling on any helpful resources, such as family, friends, support groups (other people with the same type of cancer), and professionals (social workers, psychologists, and/or psychiatrists).
References