Possible complications
If you have untreated hyperthyroidism:
- You
have an increased risk of developing heart problems such as atrial
fibrillation (an abnormal heart rhythm), cardiomyopathy (a weakened
heart), angina, and heart failure.
- If you are pregnant, you have an increased risk of developing some
pregnancy complications. For example: miscarriage, eclampsia, premature
labour, low birth weight, stillbirth, and possibly congenital
abnormality.
- You have an increased risk of developing osteoporosis (fragile bones).
With treatment, the outlook is good. Most of the symptoms and risks of complications go with successful treatment.
Who gets hyperthyroidism?
About 2 in 100 women, and 2 in 1000 men, develop hyperthyroidism at some stage of their life. It can occur at any age.
What are the causes of hyperthyroidism ?
There are various causes which include the following:
Graves' disease
Graves' disease is the
commonest cause. It can occur at any age, but is most common in women
aged 20 to 40. It can affect anyone, but there is often a family
history of the condition.
Graves' disease is an autoimmune
disease. The immune system normally makes antibodies to attack
bacteria, viruses, and other 'germs'. In autoimmune diseases, the
immune system makes antibodies against tissues of the body. If you have
Graves' disease, you make antibodies that attach to the thyroid gland.
These stimulate the thyroid to make lots of thyroxine. It is thought
that something triggers the immune system to make these antibodies. The
'trigger' is not known.
In Graves' disease the thyroid gland
usually enlarges, which causes a swelling in the neck (goitre). The
eyes are also affected in about half of cases. If they are affected,
the eyes are 'pushed' forward and look more prominent (proptosis). This
can cause discomfort and watering of the eyes. Problems with eye
muscles may also occur and lead to double vision. It is not clear why
eye symptoms occur in some people who have Graves' disease. They may be
due to the antibodies affecting the tissues around the eye.
Thyroid nodules
This is a less common cause
of hyperthyroidism. Thyroid nodules are lumps which can develop in the
thyroid gland. It is not clear why they develop. They are usually
benign (non-cancerous) but contain abnormal thyroid tissue.
The
abnormal thyroid tissue in the thyroid nodules does not respond to the
normal controlling system which ensures that you make just the right
amount of thyroxine. Therefore, if you have a thyroid nodule, you may
make more than normal amounts of thyroxine.
- Sometimes only
one nodule forms. This is called a 'toxic solitary adenoma'. This most
commonly occurs in people aged between 30 and 50.
- The thyroid may become generally lumpy or nodular. This most
commonly occurs in older people, and is called a 'toxic multi-nodular
goitre'.
Note: the word "toxic" above relating to adenomas or
multinodular goitres does not mean "poisonous". It is just one of those
medical words which refers to the hyperthyroidism.
Other causes
There are several other rare
causes of hyperthyroidism. For example, some people who take the
medicines amiodarone and lithium develop hyperthyroidism. There are
various other rare diseases that result in excess thyroxine being made.
How is hyperthyroidism diagnosed?
A blood
test can diagnose hyperthyroidism. A normal blood test will also rule
it out if symptoms suggest that it may be a possible diagnosis.
Usually, both of the following are measured in a blood sample:
-
Thyroid-stimulating hormone (TSH).
This hormone is made in the pituitary gland in the brain. It is
released into the bloodstream. It stimulates the thyroid gland to make
thyroxine. If the level of thyroxine in the blood is high, then the
pituitary releases less TSH. Therefore, a low level of TSH means the
thyroid gland is overactive and is making too much thyroxine.
-
Thyroxine (T4). A high level of T4 confirms hyperthyroidism.
Sometimes the result of the tests are 'borderline'. For
example, a normal T4 but with a low TSH. Other tests are sometimes done
to clarify the situation and the cause. For example, another blood test
called T3 is sometimes helpful and an ultrasound scan of the thyroid or
a thyroid scan may be done if you have a nodular goitre. Also, if tests
are borderline one option is to repeat the tests a few weeks later, as
sometimes borderline tests are due to another illness. Other tests may
be done if a rare cause of hyperthyroidism is suspected.
What are the treatments for hyperthyroidism?
The
main aim of treatment is to reduce the level of thyroxine to normal.
Other problems such as a large goitre (thyroid swelling) or associated
eye problems may also need treatment. Factors such as the underlying
cause of the problem, your age, and the size of any goitre are taken
into account to decide on the best treatment plan. Treatment options
include the following.
Medicines - usually carbimazole
Medicines
can reduce the amount of thyroxine made by the overactive thyroid
gland. The most common medicine used in the UK is carbimazole.
Carbimazole does not affect the thyroxine which is already made and
stored, but reduces further production. Therefore, it may take 4 to 8
weeks of treatment for your thyroxine level to come down to normal.
The
dose of carbimazole needed to keep the thyroxine level normal varies
from person to person. Carbimazole is usually taken for 12-18 months at
first. After this, in about half of cases, the condition will have
settled down and the carbimazole can be stopped. If the condition
flares up again some time in the future, a further course may be
needed. In about half of cases, carbimazole needs to be continued
long-term to control symptoms. A different treatment may then be a
better option if you do not want to take carbimazole long-term.
Warning:
carbimazole can, rarely, affect the white blood cells which fight
infection. If you develop a fever, sore throat, mouth ulcers, or other
symptoms of infection whilst taking carbimazole, stop taking the
tablets immediately and see a doctor urgently for a blood test.
Radio-iodine
This involves taking a drink,
or swallowing a capsule, which contains radioactive iodine. The main
use of iodine in the body is to make thyroxine. Therefore, the
radioactive iodine builds up in the thyroid gland. As the radioactivity
is concentrated in the thyroid gland, it destroys some thyroid tissue
which reduces the amount of thyroxine that you make. The dose of
radioactivity to the rest of the body is very low and is not dangerous.
However, it is not suitable if you are pregnant or breastfeeding. Also,
after treatment, women should not become pregnant for at least six
months, and men are advised not to father children for at least four
months.
Also, following radio-iodine treatment you should
avoid prolonged contact with others for a specified time. This may be
for 2-4 weeks, depending on the amount of radio-iodine you receive. The
aim is to limit the exposure of radioactivity to others. For the
specified period you will be advised to take precautions such as:
- Limit
contact with children. If you have children or have a job where you
have contact with children you should discuss this with the specialist
before treatment.
- Stay more than an arm’s length away from other people.
- Sleep alone.
- Avoid going to places like cinemas, theatres, pubs and restaurants where you may be in close contact with other people.
- Take some time off work if your work involves close contact with other people.
Your specialist will give detailed advice regarding these precautions.
Thyroid replacement therapy
It can be
difficult for a doctor to judge just the right dose of carbimazole, or
just the right amount of radio-iodine, to give in each case. Too much
treatment may make the thyroxine level go too low. Not enough treatment
means the level remains higher than normal. Regular blood tests are
needed to check on the thyroxine level.
One option is to
deliberately take a high dose of carbimazole each day, or to take a
one-off high dose of radio-iodine. This stops the thyroid gland making
any thyroxine. But, you can take a daily dose of thyroxine tablets to
keep the blood level of thyroxine normal. This 'over-treatment' and
taking replacement thyroxine ('block and replace') is a popular option.
Surgery
This involves removing part of the
thyroid gland. It may be a good option if you have a large goitre
(thyroid swelling) which is causing problems in the neck. If too much
thyroid is removed it is not usually a problem as you can take
thyroxine tablets to keep the thyroxine level normal. It is usually a
safe operation, but as with all operations there is a small risk.
Treatment for eye problems
You may need to
see an eye specialist if you develop the eye problems of Graves'
disease. Relatively minor symptoms affect the eyes in about half of
people with Graves' disease. Measures such as artificial tears,
sunglasses, and eye protectors whilst you sleep may be sufficient to
help.
However, about 1 in 20 people with Graves' disease have
severe eye changes. Treatment can then be more difficult and may
include surgery, radiation treatment, or steroid tablets.
Beta-blocker medicines
Some people take a
beta-blocker medicine (for example, propranolol, atenolol, etc) for a
few weeks whilst the level of thyroxine is reduced gradually by one of
the above treatments. Beta-blockers can block some of the effects of a
high level of thyroxine. In particular they help to reduce the symptoms
of tremor, palpitations, sweating, agitation, and anxiety.
Follow up
Regular checks are recommended,
even after you finish a successful treatment. The most important thing
is to have a yearly blood test to check that you have the right level
of thyroid hormone (thyroxine) in your blood. Your GP may do this test.
This is because some people become hyperthyroid again sometime in the
future. Others who have been treated successfully develop an underactive thyroid in the future. If this occurs it can usually be treated easily with thyroxine tablets.
Further help and advice
British Thyroid Foundation
PO Box 97, Clifford, Wetherby, West Yorkshire, LS23 6XD
Tel: 01423 709 707 Web: www.btf-thyroid.org
Thyroid Eye Disease (TED) Charitable Trust
PO BOX 2954, Calne, Wiltshire, SN11 8WR
Tel: 0844 800 8133 Web: www.tedct.co.uk
References
© EMIS and PiP 2008 Updated: 15 May 2008
