What is hyperthyroidism?
Hyperthyroidism is a condition in which your thyroid creates and releases more hormones than you need. This is also called overactive thyroid. The main hormones your thyroid makes include triiodothyronine (T3) and thyroxine (T4).
Hyperthyroidism can affect your entire body and is a condition that needs to be treated by a healthcare provider.
What does my thyroid do?
Located at the front of your neck, the thyroid is a butterfly-shaped gland. Glands are organs that can be found all over your body. Some of your glands create and release hormones — substances that help your body function and grow. The thyroid gland plays a big part in many of your body’s main functions, including:
- Regulating your body temperature.
- Controlling your heart rate.
- Controlling your metabolism (the process that transforms the food you put in your body into energy that helps your body function).
When your thyroid gland is working correctly, your body is in balance, and all of your systems function properly. If your thyroid stops working the way it’s meant to — creating too much or too little thyroid hormones — it can impact your entire body.
What is the difference between hyperthyroidism and hypothyroidism?
Hyperthyroidism and hypothyroidism are medical conditions that both have to do with the amount of thyroid hormone your thyroid makes and releases — the difference is how much.
Picture something related to the word “hyper.” Most likely, you just thought of something fast or full of a lot of energy. When you have hyperthyroidism, your thyroid is overactive and produces and releases too much thyroid hormone.
In the medical world, the prefix “hypo-” means “low” or “not enough.” When you have hypothyroidism, your thyroid is underactive and doesn’t make and release enough thyroid hormone that your body needs.
Who gets hyperthyroidism?
Anyone can have hyperthyroidism, but it’s more common in females.
How common is hyperthyroidism?
Hyperthyroidism is relatively rare. Approximately 1% of people in the United States have hyperthyroidism.
What are the symptoms of hyperthyroidism?
There are many symptoms of hyperthyroidism, and they can impact your entire body. You may experience some of these symptoms and not others, or many of them at the same time. Symptoms of hyperthyroidism can include:
- Rapid heartbeat (palpitations).
- Feeling shaky and/or nervous.
- Weight loss.
- Increased appetite.
- Diarrhea and more frequent bowel movements.
- Vision changes.
- Thin, warm and moist skin.
- Menstrual changes.
- Intolerance to heat and excessive sweating.
- Sleep issues.
- Swelling and enlargement of the neck from an enlarged thyroid gland (goiter).
- Hair loss and change in hair texture (brittle).
- Bulging of the eyes (seen with Graves’ disease).
- Muscle weakness.
Symptoms and Causes
What causes hyperthyroidism?
Medical conditions and situations that can cause hyperthyroidism include:
- Graves’ disease: In this disorder, your immune system attacks your thyroid. This makes your thyroid create too much thyroid hormone. Graves’ disease is a hereditary condition (passed down through a family). If a member of your family has Graves’ disease, there’s a chance others in the family could have it, too. It’s more common in people assigned female at birth than people assigned male at birth. Graves’ disease is the most common cause of hyperthyroidism, making up about 85% of cases.
- Thyroid nodules: A thyroid nodule is a lump or growth of cells in your thyroid gland. They can produce more hormones than your body needs. Thyroid nodules are rarely cancerous.
- Thyroiditis: Thyroiditis is inflammation of your thyroid gland, which may be painful or painless (silent). It may happen within a year of delivering a baby (postpartum thyroiditis). After you experience thyroiditis, your thyroid may be unable to recover, which would lead to hypothyroidism.
- Consuming excess iodine: If you’re at risk for hyperthyroidism and consume too much iodine (through your diet or medications), it can cause your thyroid to produce more thyroid hormone. Iodine is a mineral that your thyroid uses to create thyroid hormone. Receiving intravenous iodinated contrast (iodine “dye”) may also cause hyperthyroidism. Amiodarone, a medication that contains a high amount of iodine, may also cause hyperthyroidism.
Diagnosis and Tests
How is hyperthyroidism diagnosed?
Your healthcare provider can diagnose hyperthyroidism in several ways, including:
- A physical exam of your neck to see if your thyroid is larger than normal.
- Blood tests to look for high levels of thyroid hormone in your body.
- Imaging tests to look at your thyroid.
Physical exam for diagnosing hyperthyroidism
If you’re experiencing symptoms of hyperthyroidism, your healthcare provider’s may check the following during a physical exam in their office:
- Your thyroid: Your provider may gently feel your thyroid through the outside of your neck to check if it’s enlarged, bumpy or tender.
- Your eyes: Your provider may check your eyes for swelling, redness, bulging and other signs of Graves’ eye disease.
- Your heart: Your provider may use a stethoscope to listen to your heart for a rapid and/or irregular heartbeat.
- Your hands: Your provider may have you outstretch your hands to see if you have a tremor. They may also look for changes in your fingernails.
- Your skin: Your provider may feel your skin to see if it’s warm and moist.
Blood tests for diagnosing hyperthyroidism
Your healthcare provider may take a blood sample to look for high levels of thyroid hormone. This is called thyroid function testing. When you have hyperthyroidism, levels of the thyroid hormones T3 and T4 are above normal and thyroid-stimulating hormone (TSH) is lower than normal.
Imaging Tests for diagnosing hyperthyroidism
Taking a closer look at your thyroid can help your provider diagnose hyperthyroidism and the possible cause of it. Imaging tests your provider could use to examine your thyroid include:
- Radioactive iodine uptake (RAIU) test: For this test, you’ll take a small, safe dose of radioactive iodine (also called a radiotracer) by mouth to see how much of it your thyroid absorbs. After a certain amount of time — usually at six and 24 hours later — your healthcare provider will scan your neck with a device called a gamma probe to see how much of the radioactive iodine your thyroid has absorbed. If your thyroid has absorbed a lot of the radioactive iodine, it means that your thyroid gland is producing too much thyroxine (T4). If this is the case, you most likely have Graves' disease or thyroid nodules.
- Thyroid scan: This procedure is an extension of the RAIU, where in addition to measuring the absorbed amount of radioactivity by your thyroid, you’ll lie on a table with your head tilted back while a special camera (gamma camera) takes several images of your thyroid. The radioactive material makes all or certain parts of your thyroid appear “bright” on the screen. Your provider may use a thyroid scan to look for lumps or nodules on your thyroid, inflammation, swelling, goiter or thyroid cancer.
- Thyroid ultrasound: An ultrasound uses high-frequency sound waves to create images of your thyroid. It’s a non-invasive procedure that allows your provider to look at your thyroid on a screen. Your provider may use this test to look for nodules on your thyroid.
Management and Treatment
How is hyperthyroidism treated?
There are many treatment options for hyperthyroidism. Depending on the cause of your hyperthyroidism, some options may be better for you. Your healthcare provider will discuss each option with you and help you determine the best treatment plan.
Treatment options for hyperthyroidism include:
- Antithyroid drugs methimazole (Tapazole) or propylthiouracil (PTU): These drugs block the ability of your thyroid to make hormones. They offer rapid control of your thyroid.
- Radioactive iodine: Radioactive iodine is an oral medication that your overactive thyroid cells absorb. The radioactive iodine damages these cells and causes your thyroid to shrink and thyroid hormone levels to go down over a few weeks. This usually leads to permanent destruction of the thyroid, which will cure hyperthyroidism. The amount of radiation delivered by this medication is different from the amount used for the radioactive iodine uptake (RAIU) test and scan for diagnosis. Most people who receive this treatment have to take thyroid hormone drugs for the rest of their lives to maintain normal hormone levels.
- Surgery: Your healthcare provider may remove your thyroid gland through surgery (thyroidectomy). This will correct your hyperthyroidism, but it will usually cause hypothyroidism (an underactive thyroid), which requires lifelong thyroid supplements to keep hormone levels normal.
- Beta blockers: These drugs block the action of thyroid hormones on the body. They do not change the level of hormones in your blood, but they can help manage symptoms like rapid heartbeat, nervousness and shakiness that are caused by hyperthyroidism. This treatment isn’t used alone and is usually paired with another option to treat hyperthyroidism over the long term.
How long does it take to treat hyperthyroidism?
The amount of time it takes to treat hyperthyroidism can change depending on what caused it. If your healthcare provider treats your condition with antithyroid medications (methimazole or propylthiouracil) your hormone levels should drop to a healthy level in about six to 12 weeks.
Your healthcare provider may decide to give you high doses of iodine drops (not radioactive), which would normalize thyroid levels in seven to 10 days. However, this is a short-term solution, and you'll most likely need a more permanent solution like surgery. Though you may need to wait to be scheduled for thyroid surgery (thyroidectomy), this is a very effective and definitive way to treat hyperthyroidism. It’s considered a permanent solution for hyperthyroidism.
Are there any risks to hyperthyroidism treatments?
With most treatments, there are also risks of side effects. It’s important to talk to your healthcare provider and weigh all of the advantages and disadvantages before deciding on a treatment plan. Some of these risks include:
- Medication side effects: The two medications that can treat hyperthyroidism are methimazole and propylthiouracil (PTU). These drugs can cause several side effects. One rare side effect that affects less than 1% of people is potential liver damage, which may be permanent in the case of PTU. Another rare (less than 1%) but serious side effect is agranulocytosis (severe drop in white blood cell count). These side effects can happen to people of any age. In pregnant people, this medication can pass from parent to the fetus through the placenta. This could cause hypothyroidism or the development of a goiter in the fetus. Pregnant people are closely monitored because of this side effect. There’s also a possibility of an allergic reaction to these medications, which occurs in about 5% of people.
- Radioactive materials: Whenever radiation is involved, there’s a possible side effect of cancer. Currently, there’s no link between using radioactive iodine to treat hyperthyroidism and developing cancer. This is considered low-risk and unlikely. One risk that is known is between a pregnant or breastfeeding person and their baby. You shouldn’t take radioactive iodine while pregnant or breastfeeding because it can affect your baby’s thyroid gland. Sometimes, you can lose sensation in your mouth after radioactive iodine (RAI) therapy. This is common. But don’t worry — even though it can last for up to a few months, the sensation does come back to your mouth over time.
- Surgery: There are always certain risks linked to surgery, like infection and bleeding. Surgery is generally considered a very effective treatment for hyperthyroidism. In rare situations, complications like paralysis of the vocal cords (inability to speak) and damage to your parathyroid glands can happen, which results in low calcium in your blood.
After treatment, you’ll most likely need to take replacement thyroid hormone for the rest of your life. This is because some of these treatments — especially surgery — reduce your thyroid hormone levels to very low levels or eliminate this hormone by removing your thyroid. You’ll need to reintroduce the thyroid hormones back into your system by taking regular medication.
What happens if hyperthyroidism is left untreated?
Hyperthyroidism can impact many parts of your body. Different systems, ranging from your vascular system (heart) to your skeletal system (bones) can all be affected if you have an overactive thyroid.
Complications from untreated or undertreated hyperthyroidism include:
If you’re experiencing symptoms of hyperthyroidism, it’s important to see your healthcare provider so they can determine a proper diagnosis and recommend treatment.
What are the risk factors for hyperthyroidism?
Some factors that could increase your risk of developing hyperthyroidism can include:
Outlook / Prognosis
What is the outlook (prognosis) for hyperthyroidism?
Hyperthyroidism is a manageable and treatable condition, and most people do well with treatment. While some forms of treatment require you to take medication for the rest of your life, your thyroid hormone levels will be normal.
Unfortunately, untreated hyperthyroidism caused by Graves’ disease may get worse over time and cause complications. If you have Graves’ disease, ask your healthcare provider questions about how you can best manage your condition.
Can hyperthyroidism be cured?
Yes, there is a permanent treatment for hyperthyroidism. Removing your thyroid through surgery or destroying your thyroid through medication will cure hyperthyroidism. However, once your thyroid is removed or destroyed, you’ll need to take thyroid hormone replacement medications for the rest of your life. Your body still needs thyroid hormones, just not at such high levels as you have in hyperthyroidism. Though you'll need to take the medication and check in with your healthcare provider regularly, this is a manageable form of thyroid disease.
Are there complications of hyperthyroidism?
Thyroid storm (thyroid crisis or thyrotoxic crisis) is a rare but serious complication of hyperthyroidism. It happens when your thyroid makes and releases a large amount of thyroid hormone in a short amount of time. Thyroid storm is a life-threatening emergency that requires immediate medical attention.
Symptoms of thyroid storm include:
- High fever — a temperature between 104 degrees to 106 degrees Fahrenheit is common.
- Rapid heart rate (tachycardia) that can exceed 140 beats per minute.
- Feeling agitated, irritable and/or anxious.
- Congestive heart failure.
- Loss of consciousness.
A complication of Graves’ disease, one of the causes of hyperthyroidism, is called Graves’ eye disease (Graves’ ophthalmopathy). This condition can usually not be prevented. Graves’ eye disease can cause the following complications:
- Bulging eyes.
- Vision loss.
- Double vision.
- Light sensitivity.
When should I see my healthcare provider?
If you’re experiencing signs and symptoms of hyperthyroidism, it’s important to see your healthcare provider so they can assess your condition and recommend treatment.
If you’ve already been diagnosed with hyperthyroidism, you’ll likely need to see your provider regularly to make sure your treatment is working.
If you’re experiencing signs of thyroid storm, a complication of hyperthyroidism, such as a high fever and a very fast heart rate, get to the nearest hospital as soon as possible.
Frequently Asked Questions
Can hyperthyroidism cause female infertility?
One of the symptoms of hyperthyroidism can be irregular menstrual cycles (periods), which can make it difficult to get pregnant. Some people actually start reaching out to their healthcare provider because of issues becoming pregnant and then learn about a thyroid condition.
Can I develop hyperthyroidism during pregnancy?
During early pregnancy, your body needs to produce more thyroid hormones than normal to help the developing fetus. These hormones are particularly important for its brain and nervous system. Having thyroid hormone levels that are a little higher than normal is alright, but if your levels increase dramatically, your healthcare provider may need to form a treatment plan. High levels of thyroid hormones can impact not only you but also the fetus.
It can be difficult to diagnose hyperthyroidism during pregnancy because your thyroid hormone levels naturally increase and the other symptoms of pregnancy mask signs of hyperthyroidism.
What foods should be avoided with hyperthyroidism?
Eating too many iodine-rich or iodine-fortified foods in your diet may cause hyperthyroidism or make it worse in some cases.
If you have hyperthyroidism, your healthcare provider may recommend certain changes to your diet. Always consult your provider or a registered dietician before making drastic changes to your diet. If you take medication for your hyperthyroidism, always take the amount prescribed by your provider.
According to the National Institutes of Health (NIH), the recommended daily dose of iodine is about 150 micrograms (mcg). The daily dose is higher for pregnant people. A low-iodine diet requires even less.
Seafood has the most iodine. Just 1 gram of seaweed contains 23.2 micrograms (mcg), or .02 milligrams (mg).
If your provider or dietician has recommended a low-iodine diet, try to avoid the following seafood and seafood additives:
Other foods have high amounts of iodine, including:
- Milk and dairy products.
- Egg yolks.
- Iodized salt.
Is hyperthyroidism the same thing as thyrotoxicosis?
Hyperthyroidism is a type of thyrotoxicosis. Hyperthyroidism happens specifically when your thyroid gland both produces and releases excess thyroid hormone. Thyrotoxicosis happens when you have too much thyroid hormone in your body in general. You could have too much thyroid hormone by taking too much thyroid medication, for example. This would be thyrotoxicosis, not hyperthyroidism.
A note from Cleveland Clinic
Getting a new diagnosis can be stressful. The good news is that hyperthyroidism is a manageable and treatable condition. If you’re experiencing symptoms of hyperthyroidism or have certain risk factors, such as a family history of Graves’ disease, be sure to contact your healthcare provider. They can have you undergo some simple tests to see if your thyroid is making too much thyroid hormone.
Cleveland Clinic is a non-profit academic medical center. Advertising on our site helps support our mission. We do not endorse non-Cleveland Clinic products or services. Policy