The Overactive Thyroid Gland - Hyperthyroidism

Just as the thyroid gland can produce too little thyroid hormone it can on occasions produce too much, this is called hyperthyroidism. This condition is less common than hypothyroidism. It again affects women more commonly than men (because women get more autoimmune diseases) at a ratio of around 5:1. Most of those affected are relatively young.

The most common causes are Graves’ disease, toxic solitary adenoma, toxic multi-nodular goitre and thyroiditis.

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Graves’ disease

This is an auto-immune disease where the body makes antibodies that mistakenly attack its own cells. These are called auto-antibodies. They lock on to part of the thyroid cell called the TSH receptors where they have the same effect as thyroid stimulating hormone TSH. They produce activation of the thyroid cells and excessive production of thyroid hormones. These hormones spill out into the bloodstream and from there are carried all around the body producing the effects of hyperthyroidism. Graves’ disease is commonly seen in young females. It follows a relapsing course with remissions and exacerbations, but eventually the disease “burns out” as the damaged thyroid gland is no longer able to produce any more hormones, the patient then becomes hypothyroid.

What are the symptoms of Graves’ disease?

The effects of too much thyroid hormone are readily apparent and in general terms there is an increase in metabolism throughout the body. In the early stages of the disease the patient most commonly complains of anxiety and restlessness, weight loss, constantly feeling hot, and irregular periods. The inflamed thyroid gland is usually enlarged, we call this a GOITRE, the unfortunate patient also has quite marked signs of a hyperactive thyroid gland. In Graves’ disease the most obvious effects are often on the eyes which can become protuberant giving the patient a “startled” appearance.

Signs and Symptoms of Hyperthyroidism
General appearance Thin, agitated, sweaty
Hair Sparse, hair loss
Cardiovascular System Fast pulse rate (Tachycardia) Irregular Heart Beat (Atrial Fibrillation)
Hands Small muscle wasting, Tremor Thyroid acropachy (thickening of the finger tips)
Eyes Bulging of the eyes (Exophthalmos and eye lid retraction) Paralysis of the eye muscles (ophthalmoplegia) Visual Loss caused by swelling around the optic nerve
Nervous system Agitation, restlessness, Brisk reflexes
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How is Graves’ disease diagnosed

Your family doctor or endocrinologist will arrange a simple blood test to make the diagnosis. Most often in Grave’s disease it will show:

How is Graves’ disease treated?

The treatment of Graves’ disease is usually carried out by an endocrinologist, but other specialists such as Ophthalmologists, Cardiologists, Nuclear Medicine specialists and occasionally surgeons may be involved depending upon the individual patient’s symptoms. Treatment usually starts with control of symptoms. This is often done by administering a ß-blocker medication such as Propanalol.

This slows the heart rate and controls the cardiovascular side effects such as tachycardia (fast heart rate) and atrial fibrillation ( an irregular heart beat). Steroids are sometimes used to control visual problems especially if there is concern over the vision.

There are three options for the long-term control of Grave’s Disease and other causes of hyperthyroidism

The most commonly used are the anti-thyroid medications such as Neo-Mercazole, Carbimazole and Propylthiouracil (PTU). They work by blocking the conversion of iodine to thyroxine in the cells of the thyroid gland. They are taken as tablets. They are usually given for a period of 12-18 months. The common side effects of these drugs are usually mild and include skin rashes, itching and aches and pains. The more serious side-effects of agranulocytosis, a low white blood cell count making you susceptible to infection and hepatitis leading liver failure are thankfully much less common (3 out of every 1000 patients).

The major problem with anti-thyroid medication is that it mostly only works while you are taking it and therefore rarely cures the condition. Only 20-30% of patients will enter a remission after taking anti-thyroid medication, most will relapse within 6 months of stopping them. Anti thyroid medications are often used to stabilise hyperthyroidism before other more long term treatments eg Radio-iodine or surgery.

This treatment has been around since the middle of the last century. The treatment is administered by a nuclear medicine specialist. It uses a radioactive version of the iodine that the thyroid normally absorbs from the blood stream called I131  to deliver radiation to the thyroid gland and stop it from working. The radio-iodine is given as a tablet or a drink. It does mean that the patient is radio-active for a time and for that reason the treatment is usually given in a special isolation room in the hospital. Most patients stay only 3 days in the hospital but may need to avoid contact with children or pregnant women for longer than this. RAI takes 6-18 weeks to have an effect on the thyroid gland.  Side-effects are few; there may be some discomfort around the front of the neck and in the saliva glands around the jaws but this is usually mild. There are some situations where even these relatively low doses of radiation are not a good idea, for example in patients with very large goitres, patients with Graves’ related eye disease, pregnant or breast feeding patients, and in children. In these patients surgery is sometimes a better option. When RAI is used it is effective at controlling the hyperthyroidism in 85% of cases. The remaining 1:6 patients are offered a further dose of RAI 4 months later, some may be referred for surgery. Around 30% of patients will need to take thyroid hormone supplementation after treatment.
Treatment How it Works How often is it successful? Advantages Disadvantage
Anti thyroid drugs
Block producttion of T3/T4 50% relapse in 2 years Safe, none invasive Agranulocytosis-low white blood cells(1:200 patients)
Inflammatory Hepatitis
High relapse rate
I – 131
Uses targeted radiation to destroy thyroid tissue 15% Relapse Effective In-patient for 3 days
Cannot use in pregnancy or breastfeeding
(Total thyroidectomy)
Removes thyroid tissue 100% successful Extremely effective. Can be used if other methods unsuitable or do not work Hypothyroidim 100%
Hypoparathyroidsm 1-5%
Recurrent Laryyngeal Nerve palsy (1% of patients)

Some causes of hyperthyroidism for example toxic adenomas and toxic multi-nodular goitres are less likely to respond to medications or radio-iodine and surgery is more likely to be recommended for these conditions. Graves disease is the most common cause of hyperthyroidism and is usually treated with medications or RAI.  However some patients develop side effects to the medications, or relapse after medical treatment. Others eg children, pregnant or breastfeeding females or patients with severe thyroid related eye disease may be unsuitable for treatment with radio-iodine. Another category of patients who often request surgical treatment are women of childbearing age who are trying to conceive (not uncommon in this patient group) and do not wish to deal with the uncertainty, medication, radiation safety issues and  time involved in none surgical treatment especially if there is no guarantee of success (15% failure after radio-iodine).

What does surgery for hyperthyroidism involve?

Surgery in uncontrolled hyperthyroidism can be dangerous. Manipulation of the thyroid gland during surgery can literally “squeeze out “ excess thyroid hormones into the bloodstream. This may produce a condition called a “thyroid storm” with a fast, irregular heart rate, a dangerously high blood pressure and the potential for collapse and coma.  It is of the utmost importance that patients are treated by an experienced team including an endocrinologist, surgeon and anaesthetist who have the expertise and facilities to manage any problems that arise. The first step is to medically stabilise the hyperthyroidism reducing the stress on the patient’s cardiovascular and nervous systems. This is usually done with Anti-Thyroid medication and cardiac medications such as propanalol to control the heart rate and the blood pressure. Sometimes anti-thyroid medication cannot be used due to previous side effects and these patients are best stabilised with high doses of a Beta blocker in the hospital.

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Once the hyperthyroidism is stabilised the patient is planned for a Total Thyroidectomy operation. Due to the inflammatory effects of the hyperthyroidism the gland is often more swollen than usual. This means that the demands on the surgeon’s expertise are even higher than usual if complications are to be avoided. It is of the utmost importance that the surgeon is highly experienced in this form of surgery. (See Thyroid Surgery page for a detailed description).