The thyroid gland
The thyroid is a small gland in the front of your neck just below your voice box (larynx). It is made up of two parts called lobes.
What is the thyroid gland?
The thyroid is a small gland in the front of your neck, just below your voicebox (larynx). It is made up of 2 parts called lobes. The lobes are connected by a thin piece of thyroid tissue called the isthmus.
What does your thyroid gland do?
The thyroid gland is part of the endocrine system. This system makes hormones that help control the way your body functions. Your thyroid gland makes the following hormones:
- thyroxine (T4)
- triiodothyronine(T3)
- calcitonin.
Thyroid hormones T3 and T4
These hormones keep your body functioning at the right speed.
If your thyroid gland does not make enough hormones, your body’s cells work slower than normal. You usually feel tired and put on weight more easily. This is called hypothyroidism, or an underactive thyroid.
If your thyroid gland makes too many hormones, your body’s cells work faster than normal. This is called hyperthyroidism, or an overactive thyroid. You usually lose weight, feel hungrier than normal, and feel shaky and anxious. Your heartbeat may be faster than normal or irregular.
A part of your brain called the hypothalamus senses if the levels of T3 and T4 in your blood are too low. If they are, it sends thyroid-releasing hormones (TRH) into your blood. The rising level of TRH makes another gland in the brain (pituitary gland) release thyroid-stimulating hormone (TSH). TSH then stimulates the thyroid gland to produce more T3 and T4. If your brain senses that the levels of T3 and T4 are too high, it sends messages to lower the amount of TSH.
Most people with thyroid cancer have normal levels of T3 and T4.
The thyroid gland needs a regular supply of iodine to produce thyroid hormones. We get iodine from our diet. It is mainly found in fish, seafood and dairy products. Some types of salt also contain iodine, but they are not commonly used in the UK.
Calcitonin
Calcitonin helps to control the amount of calcium in the blood. It works together with another hormone called parathyroid hormone (PTH), which is made in the parathyroid glands. These are 4 very small glands behind the thyroid gland. Calcium helps:
- your muscles and nerves work
- to build strong bones
- your blood to clot.
The lymphatic system
The lymphatic system helps to protect us from infection and disease. It is made up of fine tubes called lymphatic vessels. These vessels connect to groups of small lymph nodes throughout the body. The lymphatic system drains lymph fluid from the tissues of the body before returning it to the blood.
Lymph nodes are sometimes called lymph glands. They filter bacteria (germs) and disease from the lymph fluid. When you have an infection, some lymph nodes may swell as they fight the infection.
Thyroid cancer cells can sometimes spread to the lymph nodes in the neck and chest.
About our information
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References
Below is a sample of the sources used in our thyroid cancer information. If you would like more information about the sources we use, please contact us at cancerinformationteam@macmillan.org.uk
British Medical Journal. Best Practice Guidelines, Thyroid cancer. 2020.
European Society Medical Oncology (ESMO): Thyroid cancer, Clinical Practice Guidelines for Diagnosis, Treatment and Follow-up. 2019.
National Institute for Health and Care Excellence (NICE). TA535: Lenvatinib and Sorafenib for treating differentiated thyroid cancer after radioactive iodine. 2018. www.nice.org.uk/guidance/ta535 [accessed May 2021].
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Reviewers
This information has been written, revised and edited by Macmillan Cancer Support’s Cancer Information Development team. It has been reviewed by expert medical and health professionals and people living with cancer. It has been approved by Senior Medical Editor, Professor Nick Reed, Consultant Clinical Oncologist.
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