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Overview - Overactive thyroid (hyperthyroidism)

An overactive thyroid is where the thyroid gland produces more thyroid hormones than the body needs. It is also known as hyperthyroidism or thyrotoxicosis.

If you have an overactive thyroid, it can cause serious problems that may need treatment.

An overactive thyroid can affect anyone. But it is about 10 times more common in women than men. It usually happens between ages 20 and 50.

The thyroid gland

The thyroid is a small gland in your neck. It lies in front of your windpipe (trachea). It makes hormones that affect things such as your heart rate and body temperature.

Symptoms of an overactive thyroid

An overactive thyroid can cause many symptoms, including:

  • nervousness, anxiety and irritability
  • mood swings
  • difficulty sleeping (insomnia)
  • persistent tiredness and weakness
  • sensitivity to heat
  • swelling in your neck from an enlarged thyroid gland (goitre)
  • an irregular or unusually fast heart rate (palpitations)
  • twitching or trembling
  • weight loss

Symptoms of an overactive thyroid

When to see your GP

Non-urgent advice: Contact your GP if:

  • you have symptoms of an overactive thyroid

Your GP will ask about your symptoms. They can arrange for a blood test.

This will check how well your thyroid is working.

If you have an overactive thyroid, they may send you for more tests to find out the cause.

How an overactive thyroid is diagnosed

Causes of an overactive thyroid

There are many reasons why your thyroid can become overactive.

These include:

  • Graves' disease - your immune system attacks the thyroid by mistake
  • lumps (nodules) on the thyroid
  • some medicines

Causes of an overactive thyroid

Treatments for an overactive thyroid

The main treatments are:

  • medicine to stop your thyroid producing extra thyroid hormones
  • radioiodine treatment to reduce the thyroid's ability to produce hormones
  • surgery - to remove some of the thyroid

A specialist in hormonal conditions (endocrinologist) will talk to you about the best treatments for you.

Treatment for an overactive thyroid

Further problems

An overactive thyroid can sometimes lead to further problems.

These include:

  • eye problems - such as eye irritation, double vision or bulging eyes
  • pregnancy complications - such as pre-eclampsia, premature birth or miscarriage
  • a thyroid storm - a sudden and life-threatening flare-up of symptoms

Complications of an overactive thyroid

Content supplied by the NHS and adapted for Ireland by the HSE

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This project has received funding from the Government of Ireland’s Sláintecare Integration Fund 2019 under Grant Agreement Number 123.

Page last reviewed: 20 December 2023
Next review due: 20 December 2026