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The Thyroid

Understanding the Thyroid: Functions, Disorders, and Treatments

Dr Mike Forsythe

THE AUTHOR: DR. MIKE FORSYTHE

Dr Mike Forsythe is a GP and part of the Clinical Governance team here at One Day Tests. Dr. Forsythe trained at Guy’s, King’s and St Thomas’ Medical school. He is passionate about medical education, both in training fellow medical professionals and in empowering patients to take ownership of their health and wellbeing.

The Thyroid plays an important role in our health, but do you know the functions it fulfils, the disorders that can occur, and how to diagnose & treat them?


Many are unaware of the impact of the Thyroid and according to the British Thyroid Foundation, around 1 in 20 people have a type of Thyroid Disorder. 

What is the Thyroid and what does it do?

The thyroid is a small, butterfly-shaped gland located at the front of the neck. Despite its size, it plays a crucial role in regulating metabolism, energy levels, and overall bodily functions.


The thyroid produces hormones—primarily thyroxine (T4) and triiodothyronine (T3)—which control how the body uses energy. These hormones influence vital processes such as:

  • Heart rate
  • Digestion
  • Brain function
  • Temperature regulation

The thyroid is regulated by the pituitary gland, which releases thyroid-stimulating hormone (TSH) to ensure the right balance of thyroid hormones in the body.

Types of Thyroid Disorders

Thyroid disorders generally fall into two main categories:

  • Underactive thyroid (hypothyroidism)
  • Overactive thyroid (hyperthyroidism)

Other thyroid conditions include thyroid nodules, goitre, and thyroid cancer, but the most common issues are related to hormone imbalances.

RECOMMENDED BLOOD TEST


Struggling With Fatigue, Weight Changes or Hormone Imbalance?


Get a Clear Picture of Your Thyroid Health


Our range of thyroid blood tests helps assess how well your thyroid is functioning by measuring key thyroid hormones and, in some cases, thyroid antibodies and related health markers. These tests can help investigate symptoms linked to an underactive or overactive thyroid, including tiredness, hair loss, mood changes, weight fluctuations, and feeling unusually hot or cold.


What This Test Can Help Identify


Whether you need a simple Thyroid Stimulating Hormone (TSH) check, a full thyroid hormone panel, or advanced testing including thyroid antibodies and micronutrients, our thyroid testing range can help provide a clearer understanding of your thyroid health. These tests may help identify early thyroid dysfunction, monitor existing thyroid conditions, or detect autoimmune thyroid disorders such as Hashimoto’s thyroiditis and Graves’ disease.


Our thyroid range includes the TSH Blood Test, Thyroid Function Blood Test, Thyroid Antibodies Test, and Ultimate Thyroid Function Blood Test, allowing you to choose the level of testing that best suits your symptoms and health goals.


Fast, Clear Results


Results are typically available within 1–3 working days depending on the test selected and are delivered through your secure Health Dashboard, where you can track your biomarkers over time and better understand what your results may mean for your health.


If you want to better understand your thyroid health and get clarity on ongoing symptoms, click the button below to choose the right thyroid blood test for you.

Underactive Thyroid (Hypothyroidism)

Hypothyroidism occurs when the thyroid gland does not produce enough thyroid hormones, leading to a slowdown in bodily functions. This condition can result from several causes, including:


  • Autoimmune disease (Hashimoto’s thyroiditis): The most common cause, where the immune system mistakenly attacks the thyroid.

  • Iodine deficiency: Iodine is essential for thyroid hormone production.

  • Post-thyroid surgery: Partial or total removal of the thyroid can result in hypothyroidism.

  • Radiation therapy: Used for treating thyroid cancer or other cancers in the head and neck area, which can damage the thyroid.

  • Medication: Some medications can interfere with thyroid function.

  • Pituitary gland disorders: The pituitary gland regulates the thyroid, so dysfunction can lead to hypothyroidism.



What effects can it have?

When the thyroid doesn’t produce enough hormones, the body’s metabolism slows down, leading to various health complications, including:

  • Fatigue and sluggishness

  • Weight gain due to slower metabolism

  • Depression and mood changes

  • Increased risk of heart disease due to high cholesterol levels

  • Joint pain and muscle weakness

  • Fertility issues in women


Possible Symptoms

The symptoms of hypothyroidism can develop slowly over time, making it difficult to diagnose early. Common signs include:

  • Fatigue

  • Unexplained weight gain

  • Dry skin and brittle hair

  • Cold intolerance

  • Depression or brain fog

  • Slow heart rate

  • Constipation


Treatments for Hypothyroidism

Hypothyroidism is typically treated with levothyroxine, a synthetic thyroid hormone that restores normal hormone levels. Regular monitoring through blood tests ensures that the dosage remains appropriate. 

Overactive Thyroid (Hyperthyroidism)

Hyperthyroidism occurs when the thyroid gland produces too much thyroid hormone, leading to an acceleration of bodily functions. Common causes include:

  • Graves’ disease: An autoimmune disorder that overstimulates the thyroid.

  • Thyroid nodules: Lumps in the thyroid that produce excess hormones.

  • Excessive iodine intake: Too much iodine from diet or medications can trigger hyperthyroidism.

  • Thyroiditis: Inflammation of the thyroid can lead to a temporary increase in hormone release.

What effects can it have?

An overactive thyroid speeds up metabolism, which can lead to significant health complications, such as:

  • Rapid or irregular heartbeat

  • Anxiety and nervousness

  • Unintentional weight loss

  • Heat intolerance

  • Increased risk of osteoporosis due to bone loss

  • Muscle weakness


Possible Symptoms

The symptoms of hyperthyroidism can vary but often include:

  • Rapid or irregular heartbeat

  • Unexplained weight loss

  • Tremors or shakiness

  • Excessive sweating

  • Anxiety or restlessness

  • Increased appetite

  • Insomnia


Treatments for Hypothyroidism

Treatment options depend on the severity of the condition and its underlying cause.


The main approaches include:

  • Anti-thyroid medications: These drugs reduce hormone production.

  • Radioactive iodine therapy: A common and effective treatment that destroys overactive thyroid cells.

  • Surgery (thyroidectomy): Partial or complete removal of the thyroid may be necessary in severe cases.

  • Beta-blockers: These do not treat the condition itself but help manage symptoms like a fast heart rate and tremors.

Diagnosing Thyroid Problems

Thyroid disorders are commonly diagnosed using blood tests that measure:

  • TSH (Thyroid-Stimulating Hormone): High levels indicate hypothyroidism, while low levels suggest hyperthyroidism.

  • Free T4 and Free T3: These measure the actual thyroid hormone levels in the blood.

  • Thyroid Antibody Tests: Useful for detecting autoimmune thyroid conditions like Hashimoto’s or Graves’ disease.


One Day Tests offer Thyroid function blood tests that measure all of the above... and more:

When to get tested

If you experience symptoms of thyroid dysfunction, routine screening can help diagnose problems early.


Those with a family history of thyroid disorders, autoimmune diseases, or previous neck radiation therapy might want to consider regular thyroid function tests.

One Day Tests

If you looking for a blood test to monitor a specific health condition, or just want to review your overall health, One Day Tests offer a blood testing and diagnostics services across the UK.


Why One Day Tests? Simple to answer...fast, accessible and accurate blood testing at affordable prices.


You can select a local blood testing clinic or choose our easy to use home testing kits .


With over 160 different types of blood test, including our Thyroid Function blood tests, there is a blood test waiting for you.

RECOMMENDED BLOOD TEST


Struggling With Fatigue, Weight Changes or Hormone Imbalance?


Get a Clear Picture of Your Thyroid Health


Our range of thyroid blood tests helps assess how well your thyroid is functioning by measuring key thyroid hormones and, in some cases, thyroid antibodies and related health markers. These tests can help investigate symptoms linked to an underactive or overactive thyroid, including tiredness, hair loss, mood changes, weight fluctuations, and feeling unusually hot or cold.


What This Test Can Help Identify


Whether you need a simple Thyroid Stimulating Hormone (TSH) check, a full thyroid hormone panel, or advanced testing including thyroid antibodies and micronutrients, our thyroid testing range can help provide a clearer understanding of your thyroid health. These tests may help identify early thyroid dysfunction, monitor existing thyroid conditions, or detect autoimmune thyroid disorders such as Hashimoto’s thyroiditis and Graves’ disease.


Our thyroid range includes the TSH Blood Test, Thyroid Function Blood Test, Thyroid Antibodies Test, and Ultimate Thyroid Function Blood Test, allowing you to choose the level of testing that best suits your symptoms and health goals.


Fast, Clear Results


Results are typically available within 1–3 working days depending on the test selected and are delivered through your secure Health Dashboard, where you can track your biomarkers over time and better understand what your results may mean for your health.


If you want to better understand your thyroid health and get clarity on ongoing symptoms, click the button below to choose the right thyroid blood test for you.

FREQUENTLY ASKED QUESTIONS

What is the Thyroid?

The thyroid is a small, butterfly-shaped gland situated at the front of the neck. Though tiny, it is essential for controlling metabolism, energy levels, and various bodily functions.

What is an Overactive Thyroid?

Hyperthyroidism (Overactive Thyroid) occurs when the thyroid gland produces an excess of thyroid hormones, resulting in an increased rate of bodily functions.

What is an Underactive Thyroid?

Hypothyroidism (Underactive Thyroid) happens when the thyroid gland produces insufficient thyroid hormones, causing a slowdown in bodily functions.

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