What is hyperthyroidism?

Hyperthyroidism (sometimes called thyrotoxicosis or overactive thyroid) is a condition where your thyroid gland is too active and makes too much thyroid hormone.

Your thyroid gland is in your neck, near the base of your throat. It makes hormones that help control some of your body’s metabolic functions, such as your heart rate, blood pressure, body temperature and weight.

Some people have an underactive thyroid. This is called hypothyroidism. This is a different condition to hyperthyroidism, and has different causes, symptoms and treatments.

What are the symptoms of hyperthyroidism?

If you have an overactive thyroid, you may experience symptoms that relate to your metabolism speeding up. You may:

• feel anxious or nervous
• sweat more or feel unusually hot
• have heart palpitations
• feel tired

You may also lose weight, even if you’re eating the same amount of food. You may even have an increased appetite.

Other symptoms may include:

• a large thyroid (goitre)
• breathlessness
• tremor or shakiness
• eye problems
• changes in bowel habits or menstrual patterns
• thin skin or fine, brittle hair
• difficulty sleeping

If you have Graves’ disease, you may notice that your eyeballs are swollen and protrude (bulge). This is called thyroid eye disease.

What causes hyperthyroidism?

The most common cause of hyperthyroidism in Australia is Graves’ disease. This is an autoimmune condition where your immune system tells your thyroid gland to produce too much hormone. It affects females more than males. You may be at risk of developing Graves’ disease if you have a family history of this condition or other autoimmune conditions.

Hyperthyroidism can also be caused by your thyroid becoming inflamed (called thyroiditis). This can be due to:

• your genetics
• giving birth
• viral infections
• some medicines
• taking iodine supplements

Hyperthyroidism can also happen when nodules form in your thyroid and become overactive. These nodules make too much thyroid hormone without following the usual control system of the thyroid gland.

When should I see my doctor?

See your doctor if you have any of the symptoms of hyperthyroidism. Many people live with an undiagnosed thyroid disorder. Thyroid conditions can be hard to diagnose due to many symptoms being similar to those of other health conditions.

Be sure to let your doctor know about:

• your symptoms
• your family history
• any medicines or supplements that you are taking
• any family members who have had an autoimmune or thyroid condition

If you are taking medicine for hyperthyroidism, see your doctor if you notice new symptoms or if your symptoms get worse. This might be a sign that your thyroid hormones are too low, and your doctor may need to change your dose.

How is hyperthyroidism diagnosed?

Your doctor will check your neck to see if your thyroid is larger than normal, or if there are any lumps in your neck. They will also look for other signs of an overactive thyroid such as a fast heart rate.

To diagnose hyperthyroidism, you will need to have a blood test called a thyroid function test. This test measures the level of thyroid hormones in your blood.

If your blood tests show that you have high thyroid hormone levels, your doctor will refer you to an endocrinologist. They will refer you for other tests to find the cause of your overactive thyroid. These tests may include an imaging test called a thyroid nuclear scan or an ultrasound.

How is hyperthyroidism treated?

There are several treatments for hyperthyroidism. The aim of treatment is to first reduce the amount of hormone released by your thyroid gland. Once your thyroid hormone levels are normal, treatment depends on the cause of the thyroid problem and how severe it is.

Medicines

Anti-thyroid medicines such as carbimazole can reduce the amount of hormone your thyroid makes.

Your doctor might also prescribe medicine to control your symptoms, such as medicine for a fast heart rate and palpitations. You might also need medicine for your eyes if they are affected by Graves’ disease.

Radioactive iodine

Radioactive iodine therapy involves swallowing a drink or capsule that has radioactive iodine, to shrink your thyroid. Usually only one dose is needed — it keeps working in your body for several months.

You will be able to gradually cut down your dose of anti-thyroid medicine as the radioactive iodine starts working. You may need to have your hormone levels checked regularly so your doctor can adjust your dose.

Eventually, your thyroid may shrink so much that it becomes underactive. You may need medicine to treat this.

Surgery

Part or all of your thyroid gland can be removed by surgery (called a thyroidectomy). Speak with your doctor about the risks and benefits of this procedure. Surgery can sometimes cause damage to the glands and nerves around the thyroid.

Living with hyperthyroidism

Some causes of hyperthyroidism mean that you will have to take medicine for the rest of your life.

If you have surgery to remove part of or all your thyroid gland, your doctor will prescribe you lifelong thyroid hormone replacement therapy to take daily.

If you are planning a pregnancy, pregnant or breastfeeding it is important that you speak to your doctor or endocrinologist. You may need to change your dose of medicine during these times to keep you and your baby safe.

What are the complications of hyperthyroidism?

Uncontrolled hyperthyroidism increases the risk of complications during pregnancy. Your doctor will make sure your thyroid levels are normal during this time. Some treatments can also increase the risk of some genetic abnormalities in newborns.

If your hyperthyroidism is caused by Graves’ disease, you can develop Graves’-related eye disease. You may need specialist treatment to stop any vision problems.

Thyroid hormones play a role in keeping your bones healthy and managing bone repair. If your thyroid hormone levels are too high, your body may start to break down old bone faster than it can create new bone. This increases your risk of osteoporosis.

When being treated for hyperthyroidism, there is a risk that you may develop hypothyroidism. This can happen if your levels and dose are not monitored closely by your doctor. Be sure to attend all of your health appointments.

Can hyperthyroidism be prevented?

Hyperthyroidism can’t be prevented. If you have a family history of thyroid or autoimmune conditions or develop any symptoms of an overactive thyroid, it is important to contact your doctor for testing.

Smoking has been shown to be a risk factor for Graves’ disease. If you are trying to quit smoking, help is available via Quitline on 13 7848.

If you are being treated for hyperthyroidism with medicine, it is important to have regular visits with your doctor or endocrinologist. They can make sure you are taking the right dose for you.

Resources and support

The Australian Thyroid Foundation has further information on, causes, conditions and treatments, as well as questions to ask your doctor.

Call the healthdirect helpline on 1800 022 222 at any time to speak to a registered nurse (known as NURSE-ON-CALL in Victoria) for more information and advice about thyroid disorder or thyroid medicines.

Other languages

Hormones Australia provides information in community languages on thyroid conditions.

Aboriginal and/or Torres Strait Islander peoples

Find an Aboriginal Community Controlled Health Organisation (ACCHO) or affiliate near you.