Revised 2015

Hyperthyroidism is a condition where the thyroid gland produces too much thyroid hormone for the body’s needs. It is also known as an over-active thyroid or thyrotoxicosis.

  • Hyper - means “over -“
  • Hypo - means “under -“
  • The terms "hyperthyroid" and "thyrotoxic" are interchangeable


  • Graves’ disease - the most common cause
  • A toxic nodular goitre (a goitre is an enlarged thyroid gland)
  • A solitary toxic thyroid adenoma (an adenoma is a clump of cells)
  • Thyroiditis (infection or inflammation of the thyroid gland) which is temporary

Common Symptoms

A speeding up of mental and physical processes of the whole body, such as

  • weight loss, despite an increased appetite
  • palpitations / rapid pulse
  • sweating and heat intolerance
  • tiredness and weak muscles
  • nervousness, irritability and shakiness
  • mood swings or aggressive behaviour
  • looseness of the bowels
  • warm, moist hands
  • thirst
  • passing larger than usual amounts of urine
  • itchiness
  • an enlarged thyroid gland

If the cause is Graves’ disease, you may also have thyroid eye disease. Smokers are up to eight times more likely to develop thyroid eye disease than non-smokers.


  • By a physical examination and blood tests
  • A low thyroid stimulating hormone (TSH) level with a high thyroxine (T4) level indicate hyperthyroidism

Treatment Options


Blood tests are carried out

  • every 2 - 6 months when you first start taking antithyroid drugs and every 6 - 12 months during long-term treatment with antithyroid drugs
  • frequently after radioactive iodine and surgery until stable, and once a year after that

It is well recognised that thyroid problems often run in families and if family members are unwell they should be encouraged to discuss with their own GP whether thyroid testing is warranted.

If you have questions or concerns about your thyroid disorder, you should talk to your doctor or specialist as they will be best placed to advise you. You may also contact the British Thyroid Foundation for further information and support, or if you have any comments about the information contained in this leaflet.

The British Thyroid Foundation
The British Thyroid Foundation is a registered charity: England and Wales No 1006391, Scotland SC046037

Membership Information
Quick Guides

Endorsed by:

The British Thyroid Association - medical professionals encouraging the highest standards in patient care and research

The British Association of Endocrine and Thyroid Surgeons - the representative body of British surgeons who have a specialist interest in surgery of the endocrine glands (thyroid, parathyroid and adrenal)

First issued: 2008
Revised: 2010, 2011, 2015
Our literature is reviewed every two years and revised if necessary.

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