The thyroid gland
The thyroid is a small gland in the front of the neck, just below the voicebox (larynx) near the windpipe (trachea). It is part of the endocrine system.
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.
The thyroid
Parathyroid glands
You have 4 small parathyroid glands that are attached to your thyroid gland and situated just behind it.
The thyroid gland and the parathyroid glands have similar names, but they are different and do different things. We also have information about parathyroid cancer. It is a different type of cancer and is treated differently.
Iodine and the thyroid
The thyroid is made up mainly of small clusters of cells called follicles that make and store hormones.
They also absorb and use iodine. Iodine is important for making thyroid hormones. It is absorbed in our bowel from digested food and carried in the blood to the thyroid gland. Iodine is mainly found in fish, seafood and dairy products.
The thyroid gland needs a regular supply of iodine to produce thyroid hormones.
Thyroglobulin
The thyroid cells also make a protein called thyroglobulin, which stores iodine. Depending on your treatment, you might have your thyroglobulin levels measured regularly.
Related pages
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. It sends these hormones into the blood so they can travel to different cells in the body and influence what these cells do.
Depending on what the body needs, the thyroid produces more hormones. For example, it produces more hormone when you are growing or during pregnancy.
Your thyroid gland makes the following hormones:
- triiodothyronine (T3)
- thyroxine (T4)
- calcitonin.
Thyroid hormones T3 and T4
These hormones keep your body functioning at the right speed. This is called your metabolism. It provides the body with energy for essential things like breathing and digestion.
If these thyroid hormones are not making enough hormone or too much it can cause different symptoms and the following conditions.
Hypothyroidism
If the thyroid gland does not make enough T3 and T4 hormones, your body’s cells work slower than normal. This is called hypothyroidism, or an underactive thyroid. Symptoms usually include:
- feeling tired
- putting on weight more easily.
Hyperthyroidism
If the thyroid gland makes too many hormones, your body’s cells work faster than normal. This is called hyperthyroidism, or an overactive thyroid. Symptoms usually include:
- weight loss
- feeling hungrier than normal
- feeling shaky and anxious.
Your heartbeat may be faster than normal or irregular. Most people with thyroid cancer have normal levels of T3 and T4.
If you have surgery to remove all of the thyroid gland, you will need to take thyroid hormone replacement tablets. This is to replace the hormones no longer being made by the thyroid. The NHS website has more information about hyperthyroidism and hypothyroidism.
How thyroid hormones are released
If levels of T3 and T4 are low
If levels of T3 and T4 are too high
The hypothalamus sends messages to lower the amount of thyroid-stimulating hormone (TSH).
Thyroid hormones
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.
The lymphatic system
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
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.
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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
informationproductionteam@macmillan.org.uk
National Institute for Health and Care Excellent (NICE). [NG230]. Thyroid cancer: assessment and management. Published: 19 December 2022. Available from: www.nice.org.uk/guidance
Datta, R. British Medical Journal Best Practice Guidelines, Thyroid cancer. 2023. British Medical Journal. Available from: www.bestpractice.bmj.com/topics/en-gb/263
European Society Medical Oncology (ESMO): Thyroid cancer, Clinical Practice Guidelines for Diagnosis, Treatment and Follow-up. 2019. Available from: www.annalsofoncology.org/article/S0923-7534(20)32555-2/fulltext
Date reviewed
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