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An overactive thyroid (hyperthyroidism) occurs when your thyroid gland produces too much of the thyroid hormones.

Excess levels of thyroid hormones can then speed up the body’s metabolism, triggering a range of symptoms including anxiety, hyperactivity, unexplained weight loss and sweating. If untreated, it can lead to more serious health issues.

In about three in every four cases, an overactive thyroid is caused by a condition called Graves’ disease. Learn more about the condition here.

What is Graves’ disease?

Graves’ disease is a condition that causes the immune system to attack the thyroid. It often goes undiagnosed because its symptoms can reflect a wide range of ailments.

Named after Robert Graves, the first doctor to describe this type of hyperthyroidism, it’s a complex condition that, if left untreated, can lead to heart and bone issues and (very rarely) fatal complications.

In a person suffering from Graves’ disease, the immune system incorrectly identifies the thyroid as foreign, usually causing hyperthyroidism.

What causes Graves’ disease?

The cause of Graves’ disease is unknown; both men and women can get it, but it affects women 10 times more often than men. The disease occurs in people of all ages, but most often starts in the 20s and 30s.

People who get Graves’ disease often have family members who have thyroid or other autoimmune diseases; smoking can also increase your risk of getting it.

What are the symptoms of Graves’ disease?

Most people with Graves’ disease will have the typical symptoms of hyperthyroidism: trouble sleeping, a rapid heartbeat, nervousness or irritability, fatigue and muscle weakness, sweating, and often a goitre (swollen thyroid gland).

The disease can also have an impact on the eyes. This is a common effect of Graves, because the immune system may also mistake the tissues in the back of the eye as foreign, causing them to inflame and bulge, sometimes affecting vision.

Symptoms of Graves’ disease can occur slowly or very suddenly and are sometimes confused with other health problems. Some people with Graves’ disease do not have any symptoms.

How is Graves’ disease diagnosed and treated?

Medicines called thionamides are a common treatment for an overactive thyroid. These stop your thyroid producing excess hormones. You’ll usually need to take the medicine for a month or two; in the meantime, you may be given beta-blockers to relieve your symptoms.

A highly effective way of treating Graves’ disease is Radioiodine treatment, where radiation is used to damage your thyroid, reducing the amount of hormones it can produce.

Patients are given a drink or tablet that contains a low dose of radiation, which is then absorbed by your thyroid. Most people only require a single treatment – but this isn’t suitable if you’re pregnant or breastfeeding. It’s also not suitable if your overactive thyroid is causing severe eye problems.

[Read more: Learn the symptoms of hypertension]

Very occasionally – if you have severe eye problems, or the above-mentioned treatments don’t work – surgery to remove all or part of your thyroid may be necessary.

Removing the entire thyroid gland is normally recommended, as this cures an overactive thyroid and means there’s no chance of the symptoms coming back, though the patient will then be required to take medication for the rest of their lives.