Thyroid cancer happens when abnormal cells grow uncontrollably, and form a lump or tumour. There are different types of thyroid cancer. Some grow slowly and others grow quickly. In rare cases, you can have more than one type of thyroid cancer at once. Benign thyroid nodules, also called adenomas, are not cancer.
Learn more about:
- The thyroid
- The role of thyroid hormones
- Types of thyroid cancer
- What are the risk factors?
- Who gets thyroid cancer?
The thyroid
This butterfly-shaped gland sits at the front of the throat. The thyroid has 2 halves, called lobes. These 2 lobes sit on either side of the windpipe (trachea), just below the voice box (larynx). The lobes are connected by a small band of thyroid tissue called the isthmus. Behind the thyroid are 4 small glands called the parathyroid glands.
The thyroid and the parathyroid glands make hormones that are important for how your body works.
How the thyroid works
There are 2 main types of cells in the thyroid:
| Follicular cells | These cells make and store the hormones T4 and T3, and make a protein called thyroglobulin (Tg). |
| Parafollicular cells (C-cells) | These cells make the hormone calcitonin. |
Anatomy of the thyroid
Front view
Rear view
The role of thyroid hormones
The 2 main hormones made in the thyroid are:
- T4 – thyroxine
- T3 – triiodothyronine.
To keep the body’s metabolism working properly, it is important that the thyroid makes the right amounts of T4 and T3. This balance is controlled by a hormone called thyroid-stimulating hormone (TSH), which is made in the pituitary gland, near the brain.
If levels of T4 and T3 are low, the pituitary gland makes TSH, which tells the thyroid to make more hormones. If T4 and T3 levels are too high, the pituitary gland makes less TSH.
The thyroid gland and parathyroid glands also make the hormone calcitonin, which balances calcium levels in the blood.
Underactive and overactive thyroid
Your doctor may talk to you about underactive and overactive thyroid symptoms, which are explained below:
Underactive thyroid (hypothyroidism)
Without enough thyroid hormone, your metabolism slows down.
You may:
- feel tired, sluggish, fatigued or depressed
- gain weight
- have difficulty concentrating
- be constipated
- have brittle, dry hair and skin.
In severe cases, heart problems could occur.
Overactive thyroid (hyperthyroidism)
If you have too much thyroid hormone, your metabolism speeds up.
As a result, you may:
- lose weight and have increased appetite
- feel shaky and anxious
- have rapid, strong heartbeats (palpitations).
Over time, untreated hyperthyroidism can result in loss of bone strength and problems with heart rhythm and function. can result in loss of bone strength and problems with heart rhythm and heart function.
Types of thyroid cancer
Common
| papillary |
|
| follicular |
|
Rare
| medullary |
|
| oncocytic |
|
| anaplastic |
|
What are the risk factors?
The exact cause of most thyroid cancers is not known, but some things may increase your risk.
| Radiation exposure | A small number of thyroid cancers may be from radiation therapy to the head or neck as a child; living in an area with high levels of radiation; or radiation exposure at work (e.g. medical or military). Thyroid cancer usually takes 10–20 years to develop after significant radiation exposure. |
| Family history | About 5% of thyroid cancers are linked to a family history. Having a parent, child or sibling with papillary thyroid cancer (see table, right), or an inherited genetic condition, such as familial adenomatous polyposis (FAP) or Cowden syndrome, may increase your risk. Some people inherit a faulty gene, the RET gene, that can cause familial medullary thyroid cancer (FMTC) or the thyroid condition multiple endocrine neoplasia (MEN). |
| Thyroid conditions | Having thyroid nodules, an enlarged thyroid (called a goitre) or inflammation of the thyroid (thyroiditis) only slightly increases your chance of developing thyroid cancer. |
Having too much or too little iodine can affect your thyroid function. Whether this increases the risk of thyroid cancer is still being investigated.
Who gets thyroid cancer?
About 4300 people are diagnosed with thyroid cancer each year in Australia, and rates are increasing. Women are more than twice as likely to develop thyroid cancer as men.
Although it is the most common type of cancer that affects women aged 20–24, most of the people diagnosed with thyroid cancer are women in their 40s, 50s and 60s, and men in their 50s, 60s and 70s.
→ READ MORE: Thyroid cancer symptoms
More resources
A/Prof Diana Learoyd, Endocrinologist, GenesisCare North Shore, St Leonards and University of Sydney, NSW; Sally Brooks, Senior Pharmacist, Peter MacCallum Cancer Centre, VIC; Monica Kwaczynski, 13 11 20 Consultant, Cancer Council WA; Susan Leonard, Clinical Nurse Consultant – Thyroid Cancer, Royal Brisbane and Women’s Hospital, QLD; Juliette O’Brien OAM, Consumer; Jonathan Park, Consumer; A/Prof Robert Parkyn, Breast and Endocrine Surgeon, St Andrew’s Hospital and The Queen Elizabeth Hospital, SA; A/Prof David Pattison, Director, Department of Nuclear Medicine and PET Services, Royal Brisbane and Women’s Hospital, QLD.
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