Treating overactive thyroid 

If you are diagnosed with an overactive thyroid gland (hyperthyroidism), your GP will refer you to a specialist in hormonal conditions (endocrinologist) to plan your treatment.

The most widely used treatments for an overactive thyroid are outlined below.


Thionamides, such as carbimazole and propylthiouracil, are a common treatment. They are a type of medication that stops your thyroid gland producing excess amounts of thyroxine or triiodothyronine.

As thionamides affect the production of thyroid hormone rather than their current levels, you will need to take them for several weeks before you notice an improvement (usually between four to eight weeks).

Once the production of thyroid hormones is under control, your specialist may gradually reduce your medication.

You may need to continue taking thionamides for a long time, until the condition is under control.

Around 1 in 20 people will experience side effects when they first start taking thionamides, such as:

  • itchy skin rash
  • joint pain

These side effects should pass once your body is used to the effects of the medication.

In rare cases (around 1 in 500), thionamides cause a sudden drop in white blood cells (agranulocytosis), which can make you extremely vulnerable to infection. 

Symptoms of agranulocytosis include:

If you are taking thionamides and you experience any of the symptoms above, call your GP immediately for advice and an urgent blood test. If this is not possible, call NHS 111 or your local out-of-hours service.


Beta-blockers, such as propranolol or atenolol, can relieve some of the symptoms of an overactive thyroid, including tremor (shaking and trembling), rapid heartbeat and hyperactivity.

Your specialist may prescribe you a beta-blocker while the condition is being diagnosed, or until thionamide brings your thyroid gland under control. However, beta-blockers are not suitable if you have asthma.

Beta-blockers can sometimes cause side effects, including:

Radioiodine treatment

Radioiodine treatment is a form of radiotherapy used to treat most types of overactive thyroid. Radioactive iodine shrinks your thyroid gland, reducing the amount of thyroid hormone it can produce.

Radioiodine treatment is given either as a drink or a capsule to swallow. The dose of radioactivity in the radioiodine is very low and is not harmful.

Radioiodine treatment is not suitable if you are pregnant or breastfeeding, and may not be suitable if you have eye problems, such as double vision or prominent (bulging) eyes.

Women should avoid getting pregnant for at least six months after having radioiodine treatment. Men should not father a child for at least four months after having radioiodine treatment.

Most people only require a single dose of radioiodine treatment. If a further follow-up dose is required, it is usually given 6 to 12 months after the first dosage.

A short course of thionamides treatment may be given a few weeks before radioiodine treatment, as this can lead to a more rapid relief of symptoms.

Thionamides or radioiodine?

In some cases, a particular treatment may be recommended based on factors such as your age, symptoms and the amount of extra thyroid hormone in your blood. However, there may be circumstances when you are offered a choice between a long-term course of thionamides or radioiodine treatment.

Both treatments have advantages and disadvantages.

Advantages of thionamides include:

Disadvantages of thionamides include:

  • Treatment may not be as successful as radioiodine treatment.
  • There is a higher risk of side effects.

Advantages of radioiodine treatment include:

  • Treatment is usually very successful.

Disadvantages of radioiodine treatment include:

  • There is a higher chance of your thyroid gland becoming underactive as a result of treatment.  
  • Radioiodine treatment is usually not suitable for people with additional symptoms affecting their eyes (Graves' ophthalmopathy).
  • Women have to avoid getting pregnant for at least six months, and men should not father a child for at least four months after treatment.

You should discuss the potential risks and benefits of both types of treatment with the specialist in charge of your care.


Surgery to remove all or part of the thyroid gland is known as a total or partial thyroidectomy. It is a permanent cure for recurrent overactive thyroid.

Your specialist may recommend surgery if your thyroid gland is severely swollen (a large goitre) and is causing problems in your neck.

Other reasons for surgery include:

  • A person cannot be treated with radioiodine treatment as they are pregnant and are unable or unwilling to take thionamides.  
  • A person has a severe form of Graves' ophthalmopathy.
  • The symptoms return (relapse) after a previous successful course of treatment with thionamides.

It is normally recommended that the entire thyroid gland is removed, as this means there will be no chance of a relapse.

However, you will need to take medication for the rest of your life to compensate for the lack of a functioning thyroid gland – these will be the same medications used to treat an underactive thyroid gland.

Page last reviewed: 05/08/2014

Next review due: 05/11/2016