What is thyroid disease?

Thyroid Health

Everything you need to know about thyroid disease


Emily Condon
BSc (Hons) Biological Sciences

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The thyroid produces the T4 and T3 hormones which act on almost every cell of the body and are vital in regulating metabolism. Whether it is determining how fast your heart beats or how quickly your intestines process your food, the thyroid hormones control the speed at which your body cells work.

Thyroid disorders are among the most common medical conditions, with an estimated 1 in 20 people affected by a thyroid disorder. There are a number of different thyroid conditions that can influence the normal functioning of the thyroid. 

1. Hypothyroidism (an underactive thyroid)

With an underactive thyroid, also known as hypothyroidism, the thyroid gland does not produce enough of the T4 and T3 hormones. Low thyroid hormone levels ultimately slow down the body’s metabolism.
2.  Hyperthyroidism (an overactive thyroid)

With an overactive thyroid, also known as hyperthyroidism, the thyroid makes too much T4 and T3. An excess of thyroid hormones speeds up metabolism in the body.
3. Autoimmune disease

Hashimoto’s disease which is an autoimmune disorder is the most common cause of hypothyroidism. In Hashimoto’s disease, the body’s immune system produces antibodies that target and destroy the thyroid gland, eventually leading to a decrease in thyroid hormone levels produced.
Grave’s disease is another autoimmune disease that affects the thyroid and is the most common cause of hyperthyroidism. In Grave’s disease, the body’s immune system creates antibodies that target the thyroid and increase the production of both T3 and T4. The risk for an autoimmune disease is raised if you have a family history of autoimmune disease.

4. Thyroid swelling or a "goitre"

A goitre is a swelling and inflammation of the thyroid gland causing a lump in the front of the neck. Usually, the swelling does not cause any symptoms, but occasionally a goitre may cause a tight feeling in your throat, difficulty swallowing and breathing. 

There can be many possible causes of a goitre:

  • Both an underactive and overactive thyroid may lead to the development of a goitre. 
  • Low iodine in the diet.
  • Certain medications such as lithium.
  • Having treatment that involves radiation to the head or neck area.
  • Thyroid cancer.

A doctor will examine the swollen neck and may request a thyroid function test to see how well the thyroid gland is working. They will usually also arrange an ultrasound scan to look at the structure of the thyroid. Treatment depends on what has caused the goitre.

5. Nodules

Nodules are lumps within the thyroid an individual may have a single nodule or multiple nodules within the gland. Although usually, nodules are harmless, they should be examined by a doctor to see whether they need to be treated or removed. A blood test is ideal to see if the thyroid gland is underactive or overactive. An ultrasound scan may also be used to establish the size and number of thyroid nodules present and check if they need to be removed. Treatment depends on the underlying cause. The possible causes of nodules are similar to the causes of goitre.

6. Thyroid cancer 

Thyroid cancer is a rare form of cancer in the UK and is more common in women than in men. Often survival rates for thyroid cancer are as high as once detected, the thyroid gland can be removed and followed by hormone therapy. Radioactive iodine therapy is effective at killing cancer cells in the thyroid. 

Diagnosis of thyroid disorders can be difficult, as many symptoms are similar to those of other medical conditions. A blood test is an ideal way to see how well your thyroid is working. 

Learn more about thyroid disease:

What is the thyroid?

What are the risk factors for thyroid disease?

What is hypothyroidism (an underactive thyroid)?

What is hyperthyroidism (an overactive thyroid)?

How is thyroid disease diagnosed?

Reverse T3 - what is it and do I need to test for it?

Reverse T3 - results explained

What are the symptoms of thyroid disease?

Thyroid FAQs

Medicheck your thyroid

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