Hyperthyroidism (Overactive Thyroid)

Medically Reviewed by Jennifer Robinson, MD on September 23, 2023
6 min read

Hyperthyroidism is when your thyroid -- the butterfly-shaped gland at the bottom of your neck, just above your collarbone -- makes too much of a hormone called thyroxine.

Two major hormones that affect how your body works are made in your thyroid. These are called thyroxine (T-4) and triiodothyronine (T-3).

Your thyroid controls things like how fast your heart beats and how quickly you burn calories. It releases hormones to control your metabolism (all the things your body does to turn food into energy and keep you going).

Hyperthyroidism, also known as overactive thyroid, can speed up your metabolism and cause unpleasant symptoms.

Common signs include:

If you’re an older adult, you’re more likely to have subtle symptoms like a faster heart rate or being more sensitive to warm temperatures. Or you could just feel more tired after everyday activities.

Certain medicines can mask the signs of hyperthyroidism. If you take beta-blockers to treat high blood pressure or another condition, you might not know you have it. Be sure your doctor knows about all the medications you take.

When you first get hyperthyroidism, you may feel energetic. This is because your metabolism is sped up. But over time, this increase in your metabolism can break your body down and cause you to feel tired.

Usually, hyperthyroidism develops slowly. If you’re young when you get it, the symptoms might come on suddenly.

Several conditions can cause hyperthyroidism.

Graves’ disease. This immune system disorder is the most common cause of hyperthyroidism (70% of cases). Normally, the antibodies in your blood go after bacteria, but if you have Graves’ disease, the antibodies turn on your thyroid instead. This causes the gland to make too much T-4 and T-3 thyroid hormone. Doctors aren’t sure why some people get Graves’ disease, but it tends to run in families. It’s more likely to affect women under the age of 40.

Thyroid nodules (Plummer’s disease). These lumps of tissue in your thyroid can become overactive, creating too much thyroid hormone. Plummer’s disease is more common in older people.

Thyroiditis. An infection or an immune system problem can cause your thyroid to swell and leak hormones into your bloodstream. With this condition, your thyroid is swollen for no clear reason. This is often followed by hypothyroidism, in which your thyroid doesn’t make enough hormones. These conditions are usually temporary. Thyroiditis can happen:

You can also get hyperthyroidism if you get lots of iodine in your diet (like in a medication or supplement) or from taking too much thyroid hormone medication.

About 30% of people with Graves’ disease get a condition called thyroid eye disease. It involves your vision and eyes, including the muscles and tissues around them. Symptoms include:

People with Graves’ disease may also get a rare condition called Graves’ dermopathy. It can cause redness and thickening of your skin, usually on the tops of your feet or your shins.

Your doctor will ask about your medical history and look for symptoms including a swollen thyroid, a fast pulse, moist skin, and shaking in your hands or fingers. They’ll give you tests that might include:

  • Thyroid panel. This blood test measures levels of thyroid hormones and thyroid-stimulating hormone (TSH).
  • Thyroid scan. A technician injects a small amount of radioactive iodine into your bloodstream. Your thyroid absorbs it, and a special camera takes pictures of the gland to look for nodules or other signs of problems.
  • Ultrasound. A technician runs a device called a transducer over your neck. It uses sound waves to create images of your thyroid.
  • Radioactive iodine uptake test. You swallow a small amount of radioactive iodine. A device called a gamma probe measures how much of the iodine collects in your thyroid. If this uptake is high, you probably have Graves’ disease or thyroid nodules.

Your doctor will help you decide on a treatment based on your age, your overall health, the kind of hyperthyroidism you have, and how severe it is. Your options might include:

Antithyroid drugs.Methimazole (Tapazole) and propylthiouracil (PTU) block your thyroid from making too many hormones. These medicines will typically ease your symptoms within weeks or a few months, although you will probably need to stay on them for up to 18 months to help lessen the chance of a relapse. Methimazole has less severe side effects, so it’s prescribed more often. Side effects include allergic reactions like rash or itching. Up to 3% of people who take antithyroid medications have allergic reactions. It’s rare, but these drugs can also cause your body to make fewer white blood cells, a condition called agranulocytosis. This makes you more likely to get infections. Rarely, these medicines can damage your liver, so call your doctor right away if you have symptoms like yellow skin or eyes, fatigue, a fever, sore throat, or pain in your belly.

Beta-blockers. These medications don’t treat your levels of thyroid hormone but can help with symptoms like anxiety, shaking, or a fast heartbeat. Beta-blockers affect the way thyroid hormone acts on your body. They’re most often used to treat high blood pressure. Side effects may include:

Radioactive iodine. You swallow a small amount of radioactive iodine. Overactive thyroid cells absorb it, and it destroys them. This makes your thyroid shrink and your levels of thyroid hormone go down. You might need to have this treatment more than once. Because taking this medication makes your thyroid slow down, it may also cause hypothyroidism. This is easier to treat than hyperthyroidism: You’ll take a hormone supplement once a day. It usually takes 3 to 6 months to work. Doctors have used radioactive iodine to treat hyperthyroidism for over 60 years. It’s generally considered safe, and it’s used to treat more than 70% of adults with hyperthyroidism.

Surgery. If medications aren’t a good option for you, your doctor may remove all or part of your thyroid. This is called thyroidectomy. You might need to take antithyroid medicines before the surgery to prevent complications. Afterward, you might have hypothyroidism and need to take a hormone supplement. If your parathyroid glands are also removed, you may need medication to keep the calcium levels in your blood where they should be.

This surgery comes with some risks. It can damage your vocal cords and your parathyroid glands.

If you have thyroid eye disease but your symptoms aren’t severe, you can usually manage them by avoiding bright lights and wind, raising the head of your bed, and using eye drops. Your doctor may suggest a selenium supplement. In some cases, your doctor might prescribe a medication called teprotumumab-trbw (Tepezza). It’s FDA-approved to treat the symptoms of thyroid eye disease. They might also suggest steroids or other medications to help control the swelling behind your eyes.

For some people, especially those with severe thyroid eye disease, surgery is the best option. There are two kinds that can help severe symptoms:

  • Orbital decompression surgery involves removing the bone between your sinuses and eye socket. It can make more room for your eyes so that they go back to their normal position. It can help improve your vision. There are risks to the surgery, including double vision.
  • Eye muscle surgery is sometimes used to correct double vision. It works by cutting muscles in your eyeball that are covered in scar tissue. Thyroid eye disease can cause this. The cut muscles are then reattached in a different position, which can put your eyes back in proper alignment. You may need this surgery more than once to get the right results.