40ish woman looking concerned

Thyroid cancer

Thyroid cancer affects more than 300 people in Ireland each year. It is more common in women and in people over 40.

Thyroid cancer is treated with surgery, radioactive iodine therapy and thyroid hormone therapy.

On this page:

What is thyroid cancer?

Thyroid cancer happens when cells in your thyroid change and start to grow in an abnormal way. A group of these cancer cells can form a tumour. Thyroid cancer can affect how your thyroid works and cause symptoms. 

More than 300 people are diagnosed with thyroid cancer in Ireland every year.

Diagram of thyroid, larynx (voicebox) and windpipe (trachea)

What is the thyroid and what does it do?

Your thyroid is a gland at the base of your neck, just below your Adam's apple. It sits on top of your windpipe and below your voicebox (larynx).

It is shaped like a butterfly because the gland is in 2 halves. The halves are connected by a narrow bridge of thyroid tissue called the isthmus. The 2 halves are called the lobes of the thyroid. The thyroid is part of a network of glands that make up your endocrine system.

Thyroid hormones

Your thyroid makes hormones that keep your heart rate, blood pressure, body temperature and weight at the right levels. 

The thyroid gland releases three separate hormones:

  • T3, which is known as triiodothyronine 
  • T4, which is known as thyroxine 
  • Calcitonin

The T3 and T4 hormones help regulate the body's metabolic rate. The metabolic rate is how fast the various processes of the body work, such as how quickly the body burns calories.

Excess levels of T3 and T4 in the body would make someone to feel overactive and cause them to lose weight. 

Not enough T3 and T4 would make feel someone feel 'slow' and sluggish, and cause them to gain weight.

Calcitonin helps control the levels of calcium in your blood. Calcium is a mineral that has many important functions, such as building strong bones.

More information about thyroid cancer treatment

Treatment for thyroid cancer includes surgery, radioactive iodine therapy and thyroid hormone therapy. For more information about treatments for thyroid cancer, visit our treatment page. For specific treatment information use the links below.

Looking for support?

Our cancer support section contains information and advice on coping with cancer for diagnosed patients and their loved ones.

Publications about thyroid cancer
Downloadable booklets and factsheets

Medical content updated from our 'Understanding thyroid cancer' booklet (2022) reviewed by Prof Marie Louise Healy, Consultant Endocrinologist; Cristina Domsa, Clinical Nurse Specialist Endocrinology

For more information

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