Thyrotoxicosis is a treatable condition that happens when you have too much thyroid hormone in your body. Common symptoms include unexplained weight loss and having a rapid heartbeat. The treatment for thyrotoxicosis depends on what’s causing it.
Thyrotoxicosis is a condition in which you have too much thyroid hormone in your body.
Your thyroid — the butterfly-shaped gland in the front of your neck — makes and releases two hormones: triiodothyronine (also called T3) and thyroxine (also called T4). Together, they are referred to as thyroid hormones. Your thyroid and thyroid hormones play a large role in many important bodily functions, such as your body temperature, heart rate and metabolism.
Metabolism is the pace at which your body processes things — how fast it burns the food you consume to make energy and heat. When you have thyrotoxicosis, the excess amount of thyroid hormones in your body launches your metabolism into high speed, which can cause symptoms such as a rapid heartbeat (tachycardia) and weight loss and certain complications.
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
Hyperthyroidism is a type of thyrotoxicosis. Hyperthyroidism happens specifically when your thyroid gland both produces and releases excess thyroid hormone. Hyperthyroidism is often called overactive thyroid. Thyrotoxicosis happens when you have too much thyroid hormone in your body in general. You could have too much thyroid hormone from taking too much thyroid medication, for example. This would be thyrotoxicosis, not hyperthyroidism.
Anyone can get thyrotoxicosis, but females are more commonly affected by thyrotoxicosis than males, and the likelihood of thyrotoxicosis increases with age.
Thyrotoxicosis is relatively rare. It happens to approximately 2% of females and 0.2% of males.
Symptoms of thyrotoxicosis are generally the same in mild and moderate cases, but they're usually more intense the more severe the thyrotoxicosis is.
Signs and symptoms of mild and moderate thyrotoxicosis include:
A severe case of thyrotoxicosis is called thyroid storm, or thyroid crisis. This condition is rare and requires immediate medical attention, as it can be life-threatening.
Symptoms of thyroid storm (severe thyrotoxicosis) include:
Many conditions and situations can cause thyrotoxicosis, including:
Healthcare providers diagnose someone with thyrotoxicosis if blood tests show that they have elevated thyroid hormone levels (raised thyroxine and/or triiodothyronine) and low or undetectable levels of thyroid-stimulating hormone (TSH).
If you’ve been diagnosed with thyrotoxicosis, your provider will also need to determine what’s causing it, which could lead to another diagnosis.
Your healthcare provider can use many different tests and exams to help diagnose your thyrotoxicosis and its cause, including:
If you’re experiencing symptoms of thyrotoxicosis, during a physical exam in your healthcare provider’s office they may physically check the following:
Your healthcare provider may take a blood sample to look for high levels of thyroid hormones. This is called thyroid function testing. When you have thyrotoxicosis, your levels of the thyroid hormones triiodothyronine (T3) and thyroxine (T4) are higher than usual and thyroid-stimulating hormone (TSH), a hormone your pituitary gland makes, is lower than it should be. The level of TSH in your blood is important because it signals your thyroid gland to produce thyroxine.
Taking a closer look at your thyroid can help your provider diagnose thyrotoxicosis and the possible cause of it. Imaging tests your provider could use to examine your thyroid include:
Treatment for thyrotoxicosis depends on what’s causing it. Your healthcare provider will need to determine the cause of your thyrotoxicosis in order to recommend the best treatment for you.
Treatment options for thyrotoxicosis include:
Risk factors for thyrotoxicosis include:
Most cases of thyrotoxicosis aren’t preventable. If you’re taking thyroid medication, you can prevent thyrotoxicosis by never taking more medication than your healthcare provider has prescribed you. Taking too much thyroid medication can lead to thyrotoxicosis.
The outlook for people with thyrotoxicosis is generally good. There are several effective forms of treatment and therapy for thyrotoxicosis, and just like all treatments, they all have advantages and disadvantages. Together you and your healthcare provider will determine the best treatment plan for you.
How long your thyrotoxicosis lasts depends on what’s causing it and what kind of treatment you’re taking for it. For example, if you have Graves’ disease, an autoimmune condition that causes hyperthyroidism, and it’s not treated, you’ll have thyrotoxicosis until your Graves’ disease is treated. If you have thyroiditis from a viral or bacterial infection, you may have thyrotoxicosis until your thyroiditis goes away or is treated.
Different treatments for thyrotoxicosis also take different amounts of time. Your healthcare provider will let you know when you can expect to feel better.
If thyrotoxicosis is untreated or undertreated, it can cause complications. Complications from thyrotoxicosis most commonly occur in people who have untreated hyperthyroidism, especially Graves’ disease.
Complications of thyrotoxicosis include:
If you’re experiencing symptoms of thyrotoxicosis, it’s important to see your healthcare provider so that they can figure out the cause and recommend proper treatment.
If you’ve been diagnosed with chronic thyrotoxicosis (usually a form of hyperthyroidism), it’s important to see your healthcare provider regularly to make sure your treatment is working well.
If you’ve been diagnosed with thyrotoxicosis, it may be helpful to ask your healthcare provider the following questions:
While these three conditions are all related and have to do with excess thyroid hormone, they are different.
Hyperthyroidism happens when your thyroid both makes and releases too much thyroid hormone. Hyperthyroidism is most commonly caused by an autoimmune condition called Graves’ disease or thyroid nodules.
Thyroid storm is a life-threatening complication of hyperthyroidism in which your thyroid suddenly makes and releases a large amount of thyroid hormone in a short amount of time. Thyroid storm is rare and requires immediate medical attention.
Thyrotoxicosis happens when you have too much thyroid hormone in your body in general. It can be caused by hyperthyroidism or other conditions like thyroiditis, which is when something causes your thyroid to leak thyroid hormone. Taking too much thyroid medication can also cause thyrotoxicosis.
Even though it has “toxic” in its name, most cases of thyrotoxicosis are not medical emergencies, but it’s still very important to see your healthcare provider and get treatment if you have symptoms of thyrotoxicosis.
Although it’s rare, you can have an extreme case of thyrotoxicosis called thyroid storm or thyroid crisis. It happens when your thyroid suddenly starts making and releasing large amounts of thyroid hormone. This can be life-threatening and is a medical emergency. If you’re experiencing symptoms of thyroid storm, such as feeling very agitated and confused and having a high fever, get to the nearest hospital as soon as possible.
A note from Cleveland Clinic
Although it may sound scary, thyrotoxicosis is a manageable and treatable condition. If you’re experiencing symptoms of thyrotoxicosis or have certain risk factors for getting it, be sure to contact your healthcare provider. They can have you undergo some simple tests to see if you have too much thyroid hormone in your body.
Last reviewed by a Cleveland Clinic medical professional on 08/23/2021.
Learn more about our editorial process.