Health conditions

Hyperthyroidism (overactive thyroid)

What is hyperthyroidism?

Your thyroid is an endocrine gland that secretes hormones into your bloodstream. It provides a vital function by regulating your metabolism.

Hyperthyroidism is a health condition that occurs when your thyroid gland becomes overactive and produces more thyroid hormones than you need.

When you have hyperthyroidism your metabolism speeds up, making your body work harder and faster.

It is a common condition affecting more women than men.

Terms explained

Autoimmune disorder – a condition where your own antibodies attack your body.

Causes of hyperthyroidism

There are several causes of hyperthyroidism, including:

  • nodular thyroid disease
  • thyroiditis – inflammation of the thyroid gland
  • Graves’ disease.

Graves’ disease

The most common cause of hyperthyroidism is Graves’ disease, an autoimmune disorder which is caused when your own immune system antibodies start to attack your body.

Your pituitary gland regulates the production of hormones by releasing a Thyroid Stimulating Hormone (TSH) chemical.

In Graves’ disease, your own antibodies imitate the activity of the TSH and cause your thyroid to produce too much hormone.

Graves’ disease is more commonly found in women between 20 and 40. You are more susceptible to the condition if you have family members affected by it.

In addition to hyperthyroidism symptoms, Graves’s disease symptoms include:

  • eye swelling
  • protruding eyeballs
  • goitre (an enlarged thyroid gland)
  • thyroid eye disease
  • double vision.

Signs and symptoms of hyperthyroidism

Hyperthyroidism presents a range of symptoms with most relating to the speed of your metabolism and include:

  • nervousness, anxiety, irritability and high emotions
  • high libido
  • tremors and muscle weakness
  • heat intolerance and excessive perspiration
  • fatigue and interrupted sleeping patterns
  • unexplained weight loss or weight gain
  • increased heart rate and palpitations
  • rapid pulse
  • infrequent menstrual cycles and bleeding patterns
  • difficulties getting pregnant
  • diarrhoea
  • shortness of breath, especially when exercising
  • loss of hair or hair thinning
  • enlarged thyroid gland (goitre)
  • double vision and swollen eyes.

Diagnosis of hyperthyroidism

Hyperthyroidism can be diagnosed by your doctor by testing your blood to determine your hormone levels.

In some cases your blood will also be tested for certain antibodies.

If your blood tests confirm you have hyperthyroidism, your doctor will refer you to an endocrinologist (hormone conditions specialist).

Your endocrinologist may perform further tests including scans.

Radioisotope scan

This test involves injecting a small volume of radioactive substance – iodine or sodium pertechnetate – into your blood. The test is safe and the level of radioactive substance is low.

Your neck is then scanned to detect overactive areas of your thyroid.

Ultrasound scan

An ultrasound is taken to measure the size and determine the exact location of a goitre.

Treatment of hyperthyroidism

There is no cure for hyperthyroidism although the condition is manageable.

Treatment seeks to reduce the thyroid hormones to a normal level (a status called euthyroid) to regulate your metabolism.


Depending on your specific condition, your doctor or endocrinologist may prescribe:

  • anti-thyroid medications to reduce production of thyroid hormones
  • beta-blockers to help control hyperthyroidism symptoms.

There is also the risk that your medication could lead to hypothyroidism (underactive thyroid), so you will need to have regular blood tests to ensure you are taking the correct dose.

Non-surgical procedures

Radioiodine treatment

Radioiodine is an iodine that has been made radioactive and is used to treat some thyroid conditions including thyroid cancer and most types of hyperthyroidism.

It involves taking a radioiodine capsule or drink, which is absorbed by your thyroid and as the radioactivity increases it destroys some of your thyroid tissue.

It’s important that the dosage is accurate as the treatment could cause hypothyroidism if it is too high and you may require thyroxine replacement.

Radioiodine is not suitable if you're pregnant or breastfeeding.


Surgical options include a thyroidectomy, an operation that involves the surgical removal of all or part of the thyroid gland.

A thyroidectomy is usually recommended by your doctor if:

  • other treatments have failed
  • you may have thyroid cancer
  • if you are pregnant and unable to take anti-thyroid medicines.

As with all surgery there are some risks associated with this procedure that you should discuss with your doctor.

Treatment for thyroid eye disease

If you have Graves’ disease you may also need treatment for eye disease, which is an associated health condition.

Temporary solutions include:

  • wearing sunglasses
  • using eye drops
  • keeping your head elevated while sleeping to avoid swelling.

For severe symptoms long term treatments include:

  • steroid medication
  • surgery
  • radiation therapy.

Hypothyroidism - underactive thyroid

Thyroid conditions can easily be misdiagnosed as symptoms are similar to a range of other health conditions.

If you have an overactive thyroid it’s important that you have your thyroid stimulating hormone (TSH), T4 and T3 hormone levels checked regularly.

When people are treated for hyperthyroidism they sometimes develop hypothyroidism – an underactive thyroid. This is because the medication causes the thyroid to go from overactive to underactive if the correct dose is not taken.

The difference between an underactive and an overactive thyroid is:

  • An underactive thyroid can be easily treated with hormone replacement (thyroxine) with no side effects.
  • An overactive thyroid is a potentially fatal health condition if left undiagnosed and untreated.

Where to get help

  • See your doctor
  • See your endocrinologist
  • Visit a GP after hours
  • Ring healthdirect Australia on 1800 022 222.


  • Hyperthyroidism is when your thyroid gland produces and secretes too many hormones and becomes overactive.
  • An autoimmune disorder called Graves’ disease is the most common cause of hyperthyroidism.
  • Most people with hyperthyroidism develop hypothyroidism as medication causes the thyroid to go from overactive to underactive.


Diabetes and Endocrine Health Network

This publication is provided for education and information purposes only. It is not a substitute for professional medical care. Information about a therapy, service, product or treatment does not imply endorsement and is not intended to replace advice from your healthcare professional. Readers should note that over time currency and completeness of the information may change. All users should seek advice from a qualified healthcare professional for a diagnosis and answers to their medical questions.

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