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Overactive thyroid Q&As

Published by Bupa's health information team, December 2008.

Answers to questions about overactive thyroid

This section contains answers to common questions about this topic. Questions have been suggested by health professionals, website feedback and requests via email.

 

Will an overactive thyroid affect my pregnancy?

An overactive thyroid gland (hyperthyroidism) can reduce your fertility, making it more difficult for you to conceive. It may also lead to complications during pregnancy and birth. It's important to tell your doctor if you plan to try to become pregnant so that your thyroid hormone levels can be kept under control. This is the best way to try to reduce your risk of developing complications.

If you're already pregnant, you should tell your midwife or doctor if you have had thyroid problems in the past, as these could come back during pregnancy.

Explanation

An overactive thyroid gland can interfere with your menstrual cycle, leading to irregular or infrequent periods. This may affect your ability to ovulate, making it more difficult for you to get pregnant. You're more likely to conceive if your thyroid hormones are at a healthy level which is why it's important that your overactive thyroid gland is treated successfully. If you do become pregnant with an untreated overactive thyroid gland, you're more at risk of complications, such as an increased risk of miscarriage, premature birth and your baby having a low weight at birth.

Even if your overactive thyroid gland is being treated, or has been treated successfully, you still need to take precautions if you plan to have a baby. If you have been treated with radioiodine, for example, you shouldn't get pregnant for six months afterwards as the radioiodine could damage your baby's thyroid gland. Men who have had radioiodine treatment should wait four months before fathering a child. If you have been successfully treated, there is still a chance that you could develop thyroid-related problems during or after the pregnancy, so your thyroid hormone levels should be closely monitored.

Once you're pregnant, you will be referred to an obstetrician (a doctor who specialises in pregnancy and childbirth) for specialist help to make sure that any medicines used to treat your overactive thyroid gland won't affect your pregnancy or developing baby. If you're taking antithyroid medicines such as carbimazole or propylthiouracil, you will need to be monitored carefully and regularly. The doses of the medicines may need to be lower than usual. If you're planning to breastfeed, you can still take antithyroid medicines, but your baby's development will be closely monitored and you will need to take the lowest effective dose possible.

Further information

Sources

  • UK guidelines for the use of thyroid function tests. British Thyroid Association. www.british-thyroid-association.org, accessed 14 August 2008
  • Hyperthyroidism: pregnancy and fertility. British Thyroid Foundation. www.btf-thyroid.org, accessed 14 August 2008
  • Hyperthyroidism - background information. Clinical Knowledge Summaries. http://cks.library.nhs.uk, accessed 14 August 2008
  • Management of hyperthyroidism. British Thyroid Association. www.british-thyroid-association.org, accessed 14 August 2008
  • Joint Formulary Committee, British National Formulary. 55th ed. London: British Medical Association and Royal Pharmaceutical Society of Great Britain, 2008; 376-377
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What are the dangers of an untreated overactive thyroid gland?

If you have an overactive thyroid gland, it can cause a wide range of symptoms including tiredness, weight loss, an increased heart rate and shortness of breath. If you don't get treatment, the symptoms will get worse and could become life-threatening. Therefore, it's important to seek medical help and take any prescribed treatment as directed by your doctor.

Explanation

If you don't get treatment for your overactive thyroid gland, or if it isn't treated properly, your symptoms can become much more severe. You may have extreme or sudden weight loss despite having a good appetite, fatigue (severe tiredness), sweating, heart palpitations, anxiety and poor sleep. If you're older, you may develop a fast or irregular heartbeat, shortness of breath and ankle swelling. Children with an overactive thyroid tend to be hyperactive.

A fast or irregular heartbeat (atrial fibrillation) can occur in up to one in 10 people who have an overactive thyroid gland. This can make your heart less effective at pumping blood around your body and can increase your risk of having a stroke. Atrial fibrillation can usually be successfully treated.

Hyperthyroidism can increase your risk of osteoporosis (fragile bones). The osteoporosis can be corrected once your overactive thyroid has been treated. If you're worried about your risk of osteoporosis, it's important to speak to your GP.

Graves' disease is the most common cause of hyperthyroidism and can cause eye problems (called Graves' ophthalmopathy or thyroid eye disease). If you have thyroid eye disease, it's likely that you will get minor eye irritation and puffiness around your eyes. It's possible that your eyes may appear more bulging.

If you have more severe thyroid eye disease, you may have double vision, especially as you look from side to side. This active stage usually lasts for a few months and then settles down on its own. In one in 10 people, however, the eyes get worse.

If you find that your vision is affected, it's important to talk to your doctor who will refer you to an ophthalmologist (a doctor who specialises in eye health including eye surgery). With treatment, your eyes may return to how they used to be. However, the longer you have these eye changes, the longer it takes for them to disappear with treatment - it can take up to two years for some people. If you have severe eye disease, you may be advised not to have radioiodine treatment.

If you have an overactive thyroid gland and don't get it treated, or it isn't treated properly, very rarely you may develop a life-threatening reaction called a thyroid storm (thyrotoxic crisis). This may be triggered by an infection, surgery or trauma. The symptoms can be very severe, including a very fast or irregular heartbeat, fever, dehydration, agitation and coma. You will need to get emergency treatment.

To prevent complications from an overactive thyroid gland, it's important to follow the treatment plan outlined by your GP or endocrinologist (a doctor who specialises in conditions that affect your hormones). This may involve taking prescribed antithyroid medicines, having radioiodine treatment or having surgery to remove your thyroid gland.

Further information

Sources

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I am due to start radioiodine treatment. Do I need to take any precautions?

Yes, you will need to take some precautions before and after radioiodine treatment, and your endocrinologist (a doctor who specialises in conditions that affect your hormones) will be able to advise you about these. Common precautions include stopping certain medicines before treatment and trying not to have prolonged contact with other people for a recommended amount of time after the treatment.

Explanation

Radioiodine treatment involves using radioactive iodine to destroy the overactive thyroid gland and slow down the production of the hormone thyroxine. You take the radioiodine in a drink or capsule. About eight to nine out of 10 people with hyperthyroidism are cured of the condition after a single dose of radioiodine, but the treatment can take between a few weeks and several months to work. If it hasn't worked within six months, the treatment can be repeated.

If you have been taking antithyroid medicines, you will need to stop taking them before your radioiodine treatment starts. There is some evidence that having too much iodine in your diet can reduce the effectiveness of the treatment. Therefore, two weeks before the radioiodine treatment, you may be advised to eat foods that are low in iodine, such as fresh fruit and vegetables, meat, pasta and rice. If you're taking any medicines or food supplements containing iodine, kelp (a seaweed that contains iodine) or cod liver oil, you will need to stop taking them. You should try not to eat foods that contain iodine including:

  • fish and seafood
  • glace and maraschino cherries
  • iodised table salt and sea salt
  • certain cough medicines

Try to cut down on dairy products, as these can contain some iodine. It's important that you speak to your doctor before cutting out any food groups from your diet.

You can't have the treatment if you're pregnant (or may be pregnant) or breastfeeding, as radioiodine can affect your baby's thyroid gland. Women shouldn't try to get pregnant for at least six months after the treatment to make sure the radioiodine has passed out of their system. Men shouldn't try for children for four months after the treatment. Radioiodine treatment doesn't affect female fertility, even if several doses are needed. Men are very unlikely to have problems fathering children, but there is a small risk that fertility may be affected if repeated doses are necessary. You should discuss this with your doctor.

After the treatment, your body will contain some radioactivity. The level of radioactivity will decrease daily, and drinking plenty of fluids will help to get rid of it from your body. You will usually need to stay in hospital for three to six days, but if you're given a large dose, you may have to stay in for longer.

The Royal College of Physicians has produced guidelines for people having radioiodine treatment. These include:

  • limiting your contact with children
  • staying more than an arm's length away from other people
  • sleeping alone
  • not going to places such as cinemas, pubs and restaurants
  • making sure that no one else uses your towels and face cloths
  • washing your crockery and cutlery thoroughly

Your doctor will give you a card with the details of your treatment so that you can carry this around with you. This is especially important if you're travelling through ports or on international flights for six months after the treatment. Your doctor will give you advice about how to stop your family, friends and other people from picking up too much radiation from you. How long you will need to follow the precautions will depend on how much radioiodine you were given.

You may get side-effects including symptoms of an overactive thyroid, such as palpitations and sweating, in the first few weeks after having radioiodine treatment. If your thyroid gland becomes underactive (hypothyroidism), you may be prescribed thyroxine tablets.

Further information

Sources

  • Radioiodine in the management of benign thyroid disease. Clinical guidelines. Royal College of Physicians. www.rcplondon.ac.uk, accessed 14 August 2008
  • The thyroid gland and thyroid cancer. British Thyroid Association. www.british-thyroid-association.org, accessed 14 August 2008
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Related topics

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This information was published by Bupa's health information team and is based on reputable sources of medical evidence. It has been peer reviewed by Bupa doctors. The content is intended for general information only and does not replace the need for personal advice from a qualified health professional.

Publication date: December 2008

 

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