The thyroid is a butterfly-shaped gland in the front of the neck. It is found below the voice box (larynx or Adam’s apple) and is made up of two halves, called lobes, which lie on either side of the windpipe (trachea). The lobes are connected in the middle by a small band of thyroid tissue known as the isthmus.
The thyroid gland is part of the endocrine system, which consists of a collection of glands responsible for producing the body’s hormones. Hormones are the chemical messengers that communicate with the body and bring about changes. The thyroid gland makes hormones that help control the speed of the body’s processes, such as heart rate, blood pressure, body temperature and weight – this is known as your metabolic rate.
The thyroid produces three hormones that are released into the bloodstream:
The thyroid gland needs iodine – found in foods such as seafood, iodised table salt, some mineral supplements and dairy products – to make T4 and T3.
The thyroid gland is made up of two main types of cells:
Behind the thyroid glands are the parathyroid glands. These four glands produce hormones that control the amount of calcium and phosphorus in the blood.
The thyroid gland is controlled by the pituitary gland, which is found in the brain. The pituitary gland is regulated by another gland found in the brain called the hypothalamus.
When your body needs more hormones (T4 and T3), the pituitary gland produces thyroid-stimulating hormone (TSH), which prompts the thyroid gland to produce and release more T4 and T3.
The change in thyroid hormone levels can cause changes to how your cells respond (metabolism):
Thyroid cancer develops when the cells of the thyroid gland grow and divide in a disorderly (abnormal) way.
There are several types of thyroid cancer
|Types of thyroid cancer|
|papillary hyroid cancer
|follicular thyroid cancer
|medullary thyroid cancer
|anaplastic thyroid cancer
|thyroid sarcoma or lymphoma
Thyroid cancer usually develops slowly, without many obvious signs or symptoms. However, some people experience one or more of the following:
Having a painless lump in the neck is the most common sign. However, thyroid lumps, known as nodules, are relatively common and most are benign. In about 90% of cases, a thyroid nodule is a symptom of a goitre (a benign enlarged thyroid gland) or another condition affecting the head or neck.
If you notice any of these symptoms, you should see your general practitioner (GP) as soon as possible.
A cancerous thyroid usually continues to produce hormones. However, an underactive or overactive thyroid (hypothyroidism or hyperthyroidism) is not typically a symptom of cancer.
The exact cause of thyroid cancer is unknown, but several factors are known to increase the risk of developing it.
A small number of thyroid cancer cases are due to having radiotherapy treatment as a child, or living in an area with high levels of radiation in the environment, such as a nuclear accident site. Thyroid cancer usually takes 10–20 years to develop after radiation exposure.
The most common source of radiation for the average person is an x-ray scan, however the risk of developing thyroid cancer after an x-ray is minimal.
Some people inherit a faulty gene called the RET gene, which increases their risk of developing thyroid cancer. This may occur in familial medullary thyroid cancer (FMTC) or multiple endocrine neoplasia (MEN).
If you have a family history of thyroid cancer, talk to your doctor who may refer you to a genetic counsellor or a family cancer clinic.
Having a thyroid condition, such as thyroid nodules, an enlarged thyroid (goitre) or inflammation of the thyroid, may increase your chance of developing thyroid cancer.
The thyroid needs iodine to make hormones. Iodine is found in iodised salt, dairy products, seafood and eggs. Since 2009, iodine has been added to bread in Australia to help reduce the rate of iodine deficiency.
About 2400 people are diagnosed with thyroid cancer each year in Australia. Thyroid cancer is much more common in females – it is the seventh most common cancer affecting Australian women.
The average age of a woman diagnosed with thyroid cancer is 49; the average age of a man diagnosed with thyroid cancer is 54.
Thyroid cancer cases have increased over the years. Between 1991 and 2009, cases of thyroid cancer increased by 250%†. Research is being done to determine the cause of this increase. The number may have increased because there are better ways to earlier detect small cancers that previously went undiagnosed.
† Australian Institute of Health and Welfare & Australasian Association of Cancer Registries 2012. Cancer in Australia: an overview, 2012. Cancer series no. 74. Cat. no. CAN 70. Canberra: AIHW.