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Treatment of Hyperthyroidism
Radioactive Iodine

You have been diagnosed as suffering from a condition known as ‘Hyperthyroidism’. This pamphlet aims to give you some background information to the condition, its causes and treatment options.

The thyroid gland is located in the neck. Its role is to release thyroid hormones which power the cells of the body.

‘Hyperthyroidism’ or ‘thyrotoxicosis’ (over-active thyroid) is the name given when the thyroid gland secretes more hormone than it is supposed to. Hyperthyroidism is like a car being in overdrive all the time – it can feel great to start with, but after a while everything starts to wear out or break-down!


There are many symptoms associated with hyperthyroidism. Some of the common ones are listed below. In any individual patient some features may be present to a greater extent than others: -

Loss of energy, although eventually can feel ‘overdone’ and exhausted.
Nervous, anxious, irritable.
Dislike of heat. Sweaty.
Good appetite.
Weight loss. Occasionally can eat so much that weight actually increases.
Increased heart rate – palpitations.
Muscle weakness.
Skin changes – e.g. on lower legs which can be uncomfortable.
Swelling in throat – difficulty swallowing.
Dry gritty eyes – painful protruding eyes.
Double vision.

There are two main thyroid hormones, namely Thyroxine (T4) and T3. T4 is the main hormone made by the thyroid gland, and it is converted to T3 in the tissues which themselves are more sensitive to T3. The thyroid gland is stimulated to make thyroid hormones by another hormone called thyroid stimulating hormone (TSH) which is secreted from the pituitary gland which lies at the base of the brain.


Hyperthyroidism is usually due to an ‘autoimmune’ condition. For some reason the body suddenly recognises the thyroid gland as foreign, and starts to attack it. The reason for this is unclear. However instead of destroying the gland this attack actually stimulates the thyroid gland. The thyroid gland starts to overwork and produce excess thyroid hormone.

Sometimes a nodule develops within the gland and works independently from the rest of the gland. If the nodules produce lots of thyroid hormone, then hyperthyroidism may develop. There are other rare causes of hyperthyroidism.


This is easily diagnosed with a blood test. The levels of thyroid hormones in the blood are high. The thyroid gland is usually under control of another gland called the pituitary situated at the base of the brain. It does this by releasing the hormone TSH. Since the thyroid gland has gone out of control, the pituitary tries to stimulate the thyroid as little as possible, and hence TSH levels are very low or undetectable.

1.    Treatment of hyperthyroidism

a)    Antithyroid drugs (Carbimazole (Neo-Mercazole) or Propylthiouracil).

These drugs act directly on the thyroid gland to block the production of thyroid hormones. Medication is usually started at a high dose. When the blood levels of thyroid hormones have been brought back to normal, the dose may be gradually reduced. Sometimes the dose of Carbimazole is not reduced but thyroid hormone tablets added. Treatment is usually given for 12 – 18 months and then stopped. When treatment is stopped, blood tests are performed to see if the hyperthyroid condition returns, which will occur in about half of all patients. Regrettably the condition tends to recur especially in those over the age of 45 years, also in those with a large goitre and in those with severe hyperthyroidism. Your doctor may consider that it would be better for your overall health to consider only more permanent therapy (i.e. radioactive iodine or surgery – see later).

Drug side effects: these are uncommon but include general skin rashes, itching, hair loss. There is a rare but important side effect which is due to a lowering of the blood count (white cell count). When this occurs you may become aware of a very sore throat or severe mouth ulceration. The majority of sore throats however are coincidental, and are due to a viral infection and have nothing to do with the tablets. If unsure stop the drug and contact your G.P.

If the thyroid becomes overactive again, after the drugs have been stopped, then usually the drugs are restarted to control the thyroid gland. It is likely that other options for the long-term need then to be considered (see 2 and 3).

b) Other Drugs

Other drugs called beta-blockers (e.g. Propranolol, Nadolol) can be given in the early stages to control the symptoms of hyperthyroidism. They have no effect on the thyroid gland and do not treat the cause of the problem. When the symptoms have settled these drugs are usually stopped whilst the antithyroid drugs are continued.

2.     Radioactive Iodine

This involves swallowing one capsule with a drink of water. The iodine from the capsule is concentrated in the thyroid gland and switches it off. Some patients are anxious regarding the use of radioactivity. This treatment is however very safe. It has been used for fifty years and has a good track record. (For more details ask for the information sheet on ‘Radioactive Iodine’).

After treatment patients need to be followed-up with blood tests to ensure that the gland does not remain overactive for some 10% do require a second dose. More commonly patients develop an underactive thyroid gland but this is easily treated with synthetic thyroid hormone medicines taken as tablets. About nine out of ten patients eventually, over the years, develop an underactive thyroid following radioactive iodine. A few patients can develop a tender thyroid for up to 2 weeks after radioactive iodine but this usually settles spontaneously.

3.    Surgery

The thyroid gland can be removed surgically (thyroidectomy). This produces a scar on the front of the neck which some patients may dislike, but most find acceptable. After surgery most patients develop an underactive thyroid gland and some a low blood calcium both of which require monitoring and special tablet therapy. The operation will involve being in hospital for five or so days. In some, 10% may have a recurrence of thyroid overactivity which would then require radioactive iodine, as repeat surgery is associated with risk of injury to the throat and voice box nerves. There is a separate leaflet on thyroidectomy. Please ask for this if you are interested.

Hopefully you found the information in this pamphlet useful, but please remember that your Consultant or General Practitioner is always prepared to answer any further concerns you may have.

There is a patient organisation called the British Thyroid Foundation: if you are interested, please ask for a leaflet at your next hospital visit or contact British Thyroid Foundation, PO Box 97, Clifford, Wetherby, West Yorkshire  LS23 6XD.

The British Thyroid Foundation has recently joined Thyroid Federation International, 96 Mack Street, Kingston, Ontario, Canada K7L 1N9.  The website can be found at


NHS Tayside; 2006; version 1.0

Disclaimer; no liability whatsoever is accepted for information given and all such information, especially with regard to drug usage (UK version provided), must be checked with a person’s health provider.