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What is hyperthyroidism?
Hyperthyroidism means your thyroid gland makes too much thyroid hormone. Thyroid hormone controls how your body uses energy, also called metabolism. When you have too much thyroid hormone, your metabolism speeds up. You may lose weight quickly or feel nervous and moody. Or you may have no symptoms at all.
Too much thyroid hormone can also affect your heart, muscles, bones, and cholesterol.
Hyperthyroidism can occur at any age but rarely affects children. It affects women more often than men.
Your thyroid is a gland in the front of your neck.
What causes it?
Graves' disease causes most hyperthyroidism. In Graves' disease, the body's natural defence (immune) system attacks the thyroid gland. The thyroid reacts by making too much thyroid hormone. Graves' disease often runs in families. Sometimes hyperthyroidism is caused by a swollen thyroid or small growths in the thyroid called thyroid nodules.
What are the symptoms?
You may have no symptoms of hyperthyroidism. Or, you may feel nervous, moody, weak, or tired. Other symptoms include shaking hands, feeling hot and sweaty, and losing weight, even if you are eating normally.
How is it diagnosed?
Your doctor will ask questions about your past health and your symptoms and will do a physical examination to diagnose hyperthyroidism. If your doctor thinks you may have the condition, he or she will order blood tests to see how much thyroid hormone your body is making.
How is hyperthyroidism treated?
Radioactive iodine is the most common treatment for hyperthyroidism. Most people are cured after taking one dose. It destroys part of your thyroid gland. Antithyroid medicine pills may be prescribed if your symptoms are mild. If they stop working, you may need to try radioactive iodine.
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Graves' disease is the most common cause of hyperthyroidism. In Graves' disease, the body's natural defence (immune) system attacks the thyroid gland. This causes the thyroid to make too much thyroid hormone. Graves' disease often runs in families.
Other common causes include:
- Thyroid nodules.
These are abnormal growths in the thyroid gland. They cause the thyroid gland to make too much thyroid hormone.
This condition occurs when your body makes antibodies that damage your thyroid gland. You can also get thyroiditis from a viral or bacterial infection. At first, thyroiditis may cause your thyroid levels to rise as hormone leaks out from the damaged gland. Later, levels may be low (hypothyroidism) until the gland repairs itself.
Uncommon causes of hyperthyroidism include tumours or eating foods or taking medicines that contain large amounts of iodine.
You may have no symptoms of hyperthyroidism. Or:
- You may feel nervous, moody, weak, or tired.
- Your hands may shake, your heart may beat fast, or you may have problems breathing.
- You may be hot and sweaty or have warm, red, itchy skin.
- You may have more bowel movements than usual.
- You may have fine, soft hair that is falling out.
- You may lose weight even though you eat the same or more than usual.
Some women have irregular menstrual cycles or stop having periods altogether. And some men may develop enlarged breasts.
The symptoms of hyperthyroidism are not the same for everyone. Your symptoms depend on how much hormone your thyroid gland is making, how long you have had the condition, and your age.
Graves' ophthalmopathy, also called thyroid eye disease, can be a problem caused by hyperthyroidism. It can occur before, after, or at the same time as symptoms of hyperthyroidism.
Thyroid eye disease can include eyes that bulge, are red, and are sensitive to light, and blurring or double vision. People who smoke are more likely to have these problems.
Thyroid eye disease may get worse for a time if you have radioactive iodine treatment. But the condition may get better if you take antithyroid medicine.
In rare cases, hyperthyroidism can cause a condition called thyroid storm, which can cause death. This happens when the thyroid gland releases large amounts of thyroid hormones in a short period of time.
Without treatment, hyperthyroidism can lead to:
- Weight loss. This is because your body's metabolism is faster.
- Heart problems. For example, you may have a rapid heart rate, atrial fibrillation, or heart failure.
- Bone loss and osteoporosis.
When to Call a Doctor
The most serious problem linked to hyperthyroidism is a life-threatening condition called thyroid storm.
Call 9-1-1 or other emergency services immediately if you have serious signs of thyroid storm such as shock or delirium.
Call your doctor now if you have been diagnosed with hyperthyroidism and:
- You feel very irritable.
- You have unusually high or low blood pressure compared to your normal blood pressure.
- You feel nauseated, are throwing up, or have diarrhea.
- Your heart is beating very fast or you have chest pain.
- You have a fever.
- You are confused or feel sleepy.
- You can't breathe well, or you feel very tired. These can be symptoms of heart failure.
You should also call your doctor if:
- You develop symptoms of Graves ophthalmopathy, such as bulging, reddened eyes.
- You feel very tired or weak.
- You are losing weight even though you are eating normally or more than usual.
- Your throat is swollen or you are having trouble swallowing.
Watchful waiting is a wait-and-see approach. If you think you have symptoms of hyperthyroidism, watchful waiting is not a good idea. Call your doctor if you think you may have hyperthyroidism. Early treatment may reduce your chances of having more serious problems.
Examinations and Tests
To diagnose hyperthyroidism, your doctor will ask questions about your past health and your symptoms and will do a physical examination.
If your doctor thinks you may have hyperthyroidism, he or she may order:
- A thyroid-stimulating hormone (TSH) test. This blood test measures your levels of TSH. If your TSH level is low, your doctor will want to do more tests.
- Thyroid hormone tests. These blood tests measure your levels of two types of thyroid hormones, called T3 and T4. If your levels are high, you have hyperthyroidism.
When you are being treated for this condition, your doctor will test your TSH and thyroid hormones several times a year to see how well your treatment is working.
Your doctor may also do tests that can help find the cause of your condition. These can include an antithyroid antibody test, a thyroid scan, and a radioactive iodine uptake test.
If your hyperthyroidism symptoms bother you, your doctor may give you pills called beta-blockers. These can help you feel better while you and your doctor decide what your treatment should be.
Treatment for hyperthyroidism usually starts with these treatments:
- Antithyroid medicines. These work best if you have mild hyperthyroidism, if this is the first time you are being treated for Graves' disease, if you are younger than 50, or if your thyroid gland is only swollen a little bit (small goiter). These pills do not damage your thyroid gland. But they do not always work. And you have to take them at the same time every day. If they stop working, you may need to try radioactive iodine.
- Radioactive iodine therapy. This is the most common treatment. Most people are cured after taking one dose. It destroys part of your thyroid gland, but it does not harm any other parts of your body. Radioactive iodine is often recommended if you have Graves' disease and are older than 50, or if you have thyroid nodules (toxic multinodular goiter) that are releasing too much thyroid hormone. Radioactive iodine is not used if:
- You are pregnant or you want to become pregnant within 6 months of treatment.
- You are breastfeeding.
- You have thyroiditis or another kind of hyperthyroidism that is often temporary.
If you have Graves' disease and have been taking antithyroid medicine but your hyperthyroidism has not improved, you can continue to take antithyroid medicine or you can try radioactive iodine therapy.
The kind of treatment you have depends on your age, what is causing your hyperthyroidism, how much thyroid hormone your body is making, and other medical conditions you may have. Some people need more than one kind of treatment.
Hyperthyroidism is easily treated. With treatment, you can lead a healthy life. Without treatment, hyperthyroidism can lead to serious heart problems, bone problems, and a dangerous condition called thyroid storm. So even if your symptoms are not bothering you, you still need treatment.
You may need surgery if:
- Your thyroid gland is so big that you have a hard time swallowing or breathing.
- A single large thyroid nodule is releasing too much thyroid hormone.
- You have lots of side effects from antithyroid medicines and radioactive iodine is not an option for you.
Problems with treatment
Sometimes treatment cures your hyperthyroidism but may cause hypothyroidism. Hypothyroidism is the opposite of hyperthyroidism. Instead of making too much thyroid hormone, your body is now making too little thyroid hormone. Hypothyroidism is most common after treatment with radioactive iodine. But it can also occur after surgery and sometimes after taking antithyroid medicine. If you do have hypothyroidism, you may need to take thyroid hormone medicine for the rest of your life.
- Take your medicines exactly as prescribed. You need to take the thyroid medicine at the same time each day. Call your doctor or nurse advice line if you think you are having a problem with your medicine.
- Graves' disease can make your eyes sore. Use artificial tears, eye drops, and sunglasses to protect your eyes from dryness, wind, and sun. Raise your head with pillows at night to prevent your eyes from swelling. In some cases, taping your eyelids shut at night will keep your eyes from being dry in the morning.
- Make sure you get enough calcium. Foods that are rich in calcium include milk, yogurt, cheese, and dark green vegetables.
- If you need to gain weight, ask your doctor about special diets.
- Do not eat kelp. Kelp is high in iodine, which can make hyperthyroidism worse. Kelp is commonly used in sushi and other Japanese foods. You can use iodized salt and eat bread and seafood. Try to eat a balanced diet.
- Do not use caffeine and other stimulants. These can make symptoms worse, such as a fast heartbeat, nervousness, and problems focusing.
- Do not smoke. Smoking can make your condition worse and may lead to more serious eye problems. If you need help quitting, talk to your doctor about stop-smoking programs and medicines. These can increase your chances of quitting for good.
- Lower your stress. Learn to use biofeedback, guided imagery, meditation, or other methods to relax.
- Use creams or ointments for irritated skin. Ask your doctor which type to use.
- Tell all your doctors about your condition. They need to know because some medicines contain iodine.
Antithyroid medicine is often used for hyperthyroidism. It works faster than radioactive iodine therapy. And unlike radioactive iodine, it doesn't cause lasting thyroid damage.
You also may take this medicine before you have radioactive iodine treatment or surgery. Taking it may bring your metabolism to normal, make you feel better, or reduce the chances of more serious problems.
Antithyroid medicine controls hyperthyroidism in many people. But:
- You have to take the medicine for at least 1 year.
- Your symptoms may come back after you stop taking it. Then you have to start taking it again or try a different treatment.
- There are some rare side effects. These include a rash and a low white blood cell count. A low white cell count can make it hard for your body to fight infection.
You may take beta-blockers or other medicines to treat symptoms such as a fast heartbeat or dry eyes until your thyroid improves.
When to use antithyroid medicine
Antithyroid medicine works best if:
- You have mild hyperthyroidism.
- This is the first time you're being treated for Graves' disease.
- You are younger than 50.
- Your thyroid gland is only swollen a little bit (small goiter).
The medicine is used instead of radioactive iodine if you are pregnant, breastfeeding, or trying to become pregnant.
Children are treated with antithyroid medicine. That's because experts don't know if radioactive iodine treatment is safe for children.
The medicine works much better in people who have mild disease. Up to 30 out of 100 people will have their hyperthyroidism go away after they take the medicine for 12 to 18 months.footnote 1
Surgery for hyperthyroidism is called thyroidectomy. It removes part or all of the thyroid gland. Doctors rarely use this surgery to treat hyperthyroidism. It's riskier than other treatments.
You may need surgery if:
- Your thyroid gland is so big that it's hard for you to swallow or breathe.
- You have thyroid cancer.
- Your doctor suspects that you have thyroid cancer.
- You had serious side effects from taking antithyroid medicines, and radioactive iodine isn't an option for you.
- You have a large goiter that radioactive iodine treatment didn't shrink.
- You have a single, large thyroid nodule that makes too much thyroid hormone, and radioactive iodine didn't help with the nodule.
Your doctor will have you take antithyroid medicines if you have any surgery for the condition.
After surgery, your doctor will check your thyroid hormone levels regularly. That's because you could get hypothyroidism (too little thyroid hormone).
Radioactive Iodine Treatment
Radioactive iodine is given as a liquid or capsule that you swallow. The iodine is taken up by your thyroid gland. The radioactivity in the iodine kills most or all of the tissue in your thyroid gland. But it doesn't harm any other parts of your body.
Most people are cured of hyperthyroidism after one dose of the medicine.
Radioactive iodine damages your thyroid gland. Over time, most people who take it develop hypothyroidism (having too little thyroid hormone). If you have hypothyroidism, you can replace the thyroid hormone by taking thyroid hormone medicine for the rest of your life.
Radioactive iodine shouldn't be used by children. And it shouldn't be used by women who:
- Are pregnant.
- Are breastfeeding.
- Want to become pregnant within 6 months of treatment.
- Bahn RS, et al. (2011). Hyperthyroidism and other causes of thyrotoxicosis: Management guidelines of the American Thyroid Association and American Association of Clinical Endocrinologists. Thyroid, 21(6): 593–646. Also available online: http://www.liebertonline.com/doi/full/10.1089/thy.2010.0417.
Current as of: July 28, 2021
Author: Healthwise Staff
E. Gregory Thompson MD - Internal Medicine
Kathleen Romito MD - Family Medicine
David C.W. Lau MD, PhD, FRCPC - Endocrinology
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