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Overactive thyroid (hyperthyroidism)

Repe tenga hoehe rawa

Illustration showing the thyroid gland, larynx (voice box) and trachea (windpipe)Your thyroid is a small, butterfly‑shaped gland in your neck. It produces two thyroid hormones, tri‑iodothyronine (T3) and thyroxine (T4).

Thyroid hormones help your body use energy and stay warm. They keep your brain, heart, muscles and other organs working as they should.

An overactive thyroid (hyperthyroidism) happens when your thyroid gland makes too much of these hormones. This causes your body's metabolism to speed up, which in turn can cause symptoms.

An overactive thyroid is more common in women than men and can occur at any age.

There are several causes for an overactive thyroid. Treatments include tablets, radioactive iodine and surgery.

Symptoms of an overactive thyroid

Symptoms of an overactive thyroid include:

You may also get problems with your eyes, have difficulty sleeping and diarrhoea. If you're a woman, you may notice that your periods become lighter.

If left untreated for a long time, you can develop thin bones (osteoporosis).

Causes of an overactive thyroid

Grave's disease is the commonest cause of an overactive thyroid. This is an autoimmune disease.

Your immune system usually fights off infections but when you have an autoimmune disease, your immune system attacks your own cells. Your body makes a tiny protein (antibody) that attaches to your thyroid, causing it to make too much thyroid hormone. We do not know what triggers this, but it sometimes runs in families.

Thyroid nodules (lumps) can also produce too much thyroid hormone. There can be a single nodule or several, which is known as multinodular goitre (enlarged thyroid).

Rarer causes include an inflammation of the thyroid known as thyroiditis and some medicines, such as lithium or amiodarone.

Diagnosing an overactive thyroid

A blood test measures your thyroid hormones and TSH (thyroid stimulating hormone). TSH is a hormone that controls how much thyroxine you make. It's made by your pituitary gland at the base of your brain. If your thyroid is already making too much thyroxine, your TSH will be low.

A blood test can diagnose Graves’ disease by showing thyroid antibodies. If the blood test doesn't show antibodies, you may need a radionuclide thyroid scan to determine the underlying cause of your thyroid overactivity.

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On the next page: Treating an overactive thyroid (hyperthyroidism)

Written by HealthInfo clinical advisers. Last reviewed July 2023.


See also:

Thyroid eye disease

Understanding your thyroid function results

Page reference: 70677

Review key: HITHY-49064