What is hyperthyroidism?

Hyperthyroidism is a condition where your thyroid creates and releases more hormones to your body than you need. This is also called an overactive thyroid. The main hormones made by the thyroid include triiodothyronine (T3) and thyroxine (T4). Having hyperthyroidism can impact your entire body. Picture something related to the word “hyper.” Most likely, you just thought of something that’s fast or full of a lot of energy. When you have hyperthyroidism, the extra hormones can speed up your metabolism. Metabolism is the process that transforms the food you put in your body into energy that helps your body function. When you have hyperthyroidism, your metabolism is launched into high-speed. This might cause you to feel your heart beating faster, experience anxiety and nervousness, and have an increased appetite.

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. They 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. Your thyroid gland regulates your body temperature and controls your heart rate and metabolism.

When your thyroid gland is working correctly, your body is in balance and all of your systems function properly. If your thyroid stops working in the way it’s meant to — creating too much or too little of thyroid hormones — it can impact your entire body.

Who is most likely to get hyperthyroidism?

Both men and women can have hyperthyroidism. However, it’s more commonly seen in women. Some factors that could increase your risk of developing hyperthyroidism can include:

How common is hyperthyroidism?

Hyperthyroidism happens in about 1% of people in the United States.

What causes hyperthyroidism?

There are several different medical conditions that can cause hyperthyroidism. These medical conditions can include:

  • Graves’ disease: In this disorder, your immune system attacks the thyroid. This makes the 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 women than men. 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 the thyroid gland. The nodule is able to produce more hormones than your body needs. Such nodules are rarely cancerous.
  • Thyroiditis: This is a general term that refers to swelling (inflammation) of your thyroid. This inflammation can be caused by an infection or a problem with your immune system. When the thyroid is inflamed, it can leak hormones, resulting in higher levels of hormones than your body needs. Thyroiditis can happen after the delivery of a baby (postpartum thyroiditis) or from taking drugs like interferon and amiodarone (a heart medication).
  • Iodine: If you consume too much iodine (through your diet or medications), it can actually 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.

Can I develop hyperthyroidism during or after pregnancy?

During early pregnancy, your body needs to produce more thyroid hormones than normal to help the baby develop. These hormones are particularly important for your baby’s 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 hyperthyroidism can impact not only you, but also your baby.

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.

There is also a condition called postpartum thyroiditis that happens after your baby is born. This condition can happen during the first year after birth. It’s more common in women who also have type 1 diabetes. Postpartum thyroiditis can start out as hyperthyroidism (over-producing thyroid hormones) and then shift into hypothyroidism. However, this pattern doesn’t happen to every woman with postpartum thyroiditis. If you begin having symptoms of a thyroid disease during or after pregnancy, talk to your healthcare provider.

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, nervous.
  • Weight loss.
  • Increased appetite.
  • Diarrhea and more frequent bowel movements.
  • Double vision.
  • Thin 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.

What complications of hyperthyroidism can affect my body?

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.


When you have hyperthyroidism, it may feel like your heart is beating very quickly. This rapid heartbeat is a symptom of the condition that’s caused by your fast metabolism. The body is running faster than normal when you have hyperthyroidism, making you feel like your heart is racing. Having an irregular heartbeat can increase your risk of different medical conditions, including stroke.


The bones are the support structure for your body. When you have unchecked high levels of thyroid hormones, your bones can actually become brittle. This can lead to a condition called osteoporosis.

Eyes and Skin

Hyperthyroidism can be caused by a medical condition called Graves’ disease. This disease can affect both your eyes and skin. It can cause you to have several eye problems, including:

  • Bulging eyes.
  • Vision loss.
  • Double vision and light sensitivity.
  • Redness and swelling of the eyes.

Graves’ disease can also cause your skin to become red and swollen. This is particularly noticeable on the feet and shins.

Another complication of hyperthyroidism is something called a thyroid storm (thyrotoxic crisis). This is a sudden and dramatic increase in your symptoms. When this happens, your heart may beat even faster than normal and you may develop a fever. A thyroid storm is an emergency situation.

Last reviewed by a Cleveland Clinic medical professional on 04/19/2020.


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