Hypothyroidism (underactive thyroid gland)
Hypothyroidism (underactive thyroid gland) is the term used to describe a condition in which there is a reduced level of thyroid hormone (thyroxine) in the body. This can cause various symptoms, the most common being: tiredness, weight gain, constipation, aches, dry skin, lifeless hair and feeling cold. Treatment is usually easy by taking a tablet each day to replace the missing thyroxine. Treatment usually works well and symptoms usually go.
What is hypothyroidism?
Thyroxine is a hormone (body chemical) made by the thyroid gland in the neck. It is carried round the body in the bloodstream. It helps to keep the body's functions (the metabolism) working at the correct pace. Many cells and tissues in the body need thyroxine to keep them going correctly.
Hypothyroidism results from the thyroid gland being unable to make enough thyroxine, which causes many of the body's functions to slow down. Hypothyroidism may also occur if there is not enough thyroid gland left to make thyroxine, eg after surgical removal or injury.
(In contrast, if you have hyperthyroidism, you make too much thyroxine. This causes many of the body's functions to speed up.)
What are the symptoms of hypothyroidism?
Many symptoms can be caused by a low level of thyroxine. Basically, many body functions slow down. Not all symptoms develop in all cases.
However, all these symptoms can be caused by other conditions, and sometimes the diagnosis is not obvious. Symptoms usually develop slowly, and gradually become worse over months or years as the level of thyroxine in the body gradually falls.
What are the possible complications of hypothyroidism?
If you have untreated hypothyroidism:
However, with treatment, the outlook is excellent. With treatment, symptoms usually go, and you are very unlikely to develop any complications.
Who gets hypothyroidism?
About 1 in 50 women, and about 1 in 1,000 men develop hypothyroidism at some time in their life. It most commonly develops in adult women, and becomes more common with increasing age. However, it can occur at any age and can affect anyone.
What causes hypothyroidism?
Autoimmune thyroiditis - the common cause in the UK
The most common cause is due to an autoimmune disease called autoimmune thyroiditis. The immune system normally makes antibodies to attack bacteria, viruses, and other germs. If you have an autoimmune disease, the immune system makes antibodies against certain tissues of your body.
With autoimmune thyroiditis, you make antibodies that attach to your own thyroid gland, which affect the gland's function. The thyroid gland is then not able to make enough thyroxine, and hypothyroidism gradually develops. It is thought that something triggers the immune system to make antibodies against the thyroid. The trigger is not known.
Autoimmune thyroiditis is more common than usual in people with:
Some people with autoimmune thyroiditis also develop a swollen thyroid gland (goitre). Autoimmune thyroiditis with a goitre is called Hashimoto's disease. Also, people with autoimmune thyroiditis have a small increased risk of developing other autoimmune conditions such as vitiligo, pernicious anaemia, etc.
Surgery or radioactive treatment to the thyroid gland
These are common causes of hypothyroidism in the UK, due to increasing use of these treatments for other thyroid conditions.
Other causes of hypothyroidism include:
How is hypothyroidism diagnosed?
A blood test can diagnose hypothyroidism. A normal blood test will also rule it out if symptoms suggest that it may be a possible diagnosis. One or both of the following may be measured:
Note: some people have a raised TSH level but have a normal T4 level. This means that you are making enough thyroxine but the thyroid gland is needing extra stimulation from TSH to make the required amount of thyroxine. In this situation you have an increased risk of developing hypothyroidism in the future. Your doctor may advise a repeat blood test every so often to see if you do eventually develop hypothyroidism.
Other tests are not usually necessary unless a rare cause of hypothyroidism is suspected. For example, tests of the pituitary gland may be done if both the TSH and T4 levels are low.
How is hypothyroidism treated?
The treatment is to take levothyroxine (thyroxine) tablets each day. This replaces the thyroxine which your thyroid gland is not making. Most people feel much better soon after starting treatment. Ideally, take the tablet on an empty stomach (before breakfast). This is because some foods rich in calcium or iron may interfere with the absorption of levothyroxine from the gut. (For the same reason, don't take levothyroxine tablets at the same time of day as calcium or iron tablets.)
What is the dose of levothyroxine?
Most adults need between 50 and 150 micrograms daily. A low dose is sometimes prescribed at first, especially in those aged over 60 or with heart problems, and is then gradually increased over a period of time. Blood tests are usually taken every 2-3 months, and the dose may be adjusted accordingly. The blood test measures TSH (see above). Once the blood TSH level is normal it means you are taking the correct amount of levothyroxine. It is then common practice to check the TSH blood level once a year. The dose may need adjustment in the early stages of pregnancy. Also, as you get into late middle age and older, you may need a reduced dose of levothyroxine.
Missed a tablet?
Everyone forgets to take their tablets from time to time. Don't worry as it is not dangerous to miss the odd forgotten levothyroxine tablet. If you forget to take a dose, take it as soon as you remember if this is within 2 or 3 hours of your usual time. If you do not remember until after this time, skip the forgotten dose and take the next dose at the usual time. Do not take two doses together to make up for a missed dose. However, you should try to take levothyroxine regularly each morning for maximum benefit.
How long is the treatment for?
For most people, treatment is for life. Occasionally, the disease process reverses. This is uncommon, apart from the following:
Are there any side-effects or problems from treatment?
Usually not. Levothyroxine tablets replace the body's natural hormone, so side-effects are uncommon. However, if you have angina, you may find that your angina pains become worse when you first start levothyroxine. Tell a doctor if this happens.
If you take too much levothyroxine it can lead to symptoms and problems of an overactive thyroid - for example, palpitations, diarrhoea, irritability, and sweating - and increase the risk of developing osteoporosis. This is why you need blood tests to check that you are taking the correct dose.
Other medicines may interfere with the action of levothyroxine - for example: carbamazepine, iron tablets, phenytoin, and rifampicin. If you start any of these medicines, or change the dose, then you may need to alter the dose of the levothyroxine. Your doctor will advise. Also, if you take warfarin, the dose may need to be altered if you have a change in your dose of levothyroxine.
If you have hypothyroidism, you are entitled to free prescriptions. This is for all your medicines, whether related to the hypothyroidism or not. Ask at your GP surgery for a form to fill in (form FP92A) to claim this benefit.
Hyperthyroidism (over reactive thyroid)
Hyperthyroidism means a raised level of thyroid hormone. There are various causes. Graves' disease is the most common cause. Hyperthyroidism can produce various symptoms. Treatment is usually effective. Treatment options to reduce the thyroxine level include: medicines, radioiodine and surgery. Beta-blockers can ease some of the symptoms. Long-term follow-up is important, even after successful treatment.
What is hyperthyroidism?
Thyroxine is a body chemical (hormone) made by the thyroid gland. It is carried around the body in the bloodstream. It helps to keep the body's functions (the metabolism) working at the correct pace. Many cells and tissues in the body need thyroxine to keep them going correctly.
Hyperthyroidism means an overactive thyroid gland. When your thyroid gland is overactive it makes too much thyroxine. The extra thyroxine causes many of your body's functions to speed up. (In contrast, if you have hypothyroidism, you make too little thyroxine; this causes many of the body's functions to slow down.)
Thyrotoxicosis is a term that may be used by doctors instead of hyperthyroidism. The two terms mean much the same.
What are the symptoms of hyperthyroidism?
The following are symptoms of hyperthyroidism:
Most people with hyperthyroidism do not have all the symptoms but a combination of two or more is common. Symptoms usually develop slowly over several weeks. All the symptoms can be caused by other problems and so the diagnosis may not be obvious at first. Symptoms may be mild to start with but become worse as the level of thyroxine in the blood gradually rises.
If you have untreated hyperthyroidism:
With treatment, the outlook is good. With successful treatment, most of the symptoms and risks of complications go.
Who gets hyperthyroidism?
It is more common in women. About 8 in 100 women and 1 in 100 men develop hyperthyroidism at some stage of their lives. It can occur at any age.
What are the causes of hyperthyroidism?
There are various causes which include the following:
This is the most common cause. It can occur at any age but is most common in women aged 20 to 50 years. It can affect anyone but there is often a family history of the condition. There may also be family members with other autoimmune diseases (for example, diabetes, rheumatoid arthritis and myasthenia gravis).
Graves' disease is also an autoimmune disease. The immune system normally makes antibodies (tiny proteins that travel in the bloodstream) 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. The eyes are also affected in about half of cases. If they are affected, the eyes are pushed forwards 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.
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 too much thyroxine.
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.
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 conditions 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. One or both of the following may be measured in a blood sample:
Sometimes the results 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 that measures 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.
In people with Graves' disease a blood test may detect specific autoantibodies which are commonly raised. However, these can also be raised in some people without Graves' disease so this is not a specific test for Graves' disease.
What are the treatments for hyperthyroidism?
The main aim of treatment is to reduce your 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. A high dose is usually given initially which is then reduced as your thyroxine levels come down.
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. However, in these cases an alternative treatment (for example, radioactive iodine) is often recommended. 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 your white blood cells which fight infection. If you develop a fever, sore throat, mouth ulcers or other symptoms of infection whilst taking carbimazole, you should stop taking it and see a doctor urgently for a blood test.
An alternative medication called propylthiouracil is usually given instead of carbimazole if you are pregnant or breast-feeding.
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 breast-feeding. In addition, 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 radioiodine treatment, you should avoid prolonged contact with others for a specified time. This may be for 2-4 weeks, depending on the amount of radioiodine 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:
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 radioiodine, to give in each case. Too much treatment may make your thyroxine level go too low. Not enough treatment means your level remains higher than normal. Regular blood tests are needed to check on the thyroxine level.
One option is to take a high dose of carbimazole each day deliberately, or to receive a one-off high dose of radioiodine. This stops your thyroid gland making any thyroxine. You will then need to take a daily dose of thyroxine tablets to keep your blood level of thyroxine normal. This over-treatment and then taking replacement thyroxine is also called 'block and replace'.
This involves removing part of your thyroid gland. It may be a good option if you have a large thyroid swelling (goitre) which is causing problems in your neck. If too much thyroid tissue is removed then you will be given thyroxine tablets to keep your 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.
If you smoke then it is important that you try to stop. Smoking can actually make your eye problems worse.
Some people are given a beta-blocker medicine for a few weeks whilst the level of thyroxine is reduced gradually by one of the above treatments. Beta-blockers can help to reduce symptoms of tremor, palpitations, sweating, agitation and anxiety.
Regular checks are recommended, even after you finish a successful treatment. It is very important to have a regular blood test (at least every year) 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 at some time 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.
means a raised level of thyroid hormone. There are various causes. Graves' disease is the most common cause. Hyperthyroidism can produce various symptoms. Treatment is usually effective. Treatment options to reduce the thyroxine level include: medicines, radioiodine and surgery. Beta-blockers can ease some of the symptoms. Long-term follow-up is important, even after successful treatment.