Thyrotoxicosis is a treatable condition that happens when you have too much thyroid hormone in your body. Common symptoms include unexplained weight loss, a rapid heart rate and shakiness. The treatment for thyrotoxicosis depends on what’s causing it.


What is thyrotoxicosis?

Thyrotoxicosis happens when you have too much thyroid hormone in your body.

Thyroid hormone is the hormone that controls your body’s metabolism — the process in which your body transforms the food you eat into energy. With thyrotoxicosis, your metabolism becomes too fast, causing symptoms that can affect your entire body. You may feel like your body’s in overdrive or that you don’t have control over it.

An overactive thyroid gland (hyperthyroidism) is the most common cause of thyrotoxicosis. But there are other ways you can have too much thyroid hormone in your body.

Is thyrotoxicosis life-threatening?

Despite having the word “toxic” in its name, only severe cases of thyrotoxicosis are life-threatening. This is called thyroid storm (thyroid crisis), and it’s rare. A sudden event or illness (like surgery or an infection) is the most common trigger of thyroid storm. It can also happen if you’re on anti-thyroid medication and suddenly stop taking it.

It’s still important to get treatment for mild to moderate thyrotoxicosis, though. Untreated or undertreated thyrotoxicosis can lead to certain health issues.


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Symptoms and Causes

Symptoms of thyrotoxicosis include unexplained weight loss, rapid heart rate, shakiness, increased sweating and more.
Thyrotoxicosis happens when you have too much thyroid hormone in your body.

What are the symptoms of thyrotoxicosis?

Symptoms of thyrotoxicosis are generally the same in mild and moderate cases. But they’re more intense the more severe the thyrotoxicosis is.

Signs and symptoms of mild and moderate thyrotoxicosis include:

It’s important to see your healthcare provider if you have these symptoms.

A severe case of thyrotoxicosis is a thyroid storm, or thyroid crisis. It’s rare. But it’s life-threatening and requires immediate medical attention.

Symptoms of thyroid storm are more intense. For example, your heart rate may be over 140 beats per minute, and you may feel very agitated and confused. You may also have a high fever and even lose consciousness.

What causes thyrotoxicosis?

Many conditions and situations can cause thyrotoxicosis, including:

  • Hyperthyroidism: Hyperthyroidism happens when your thyroid makes and releases too much thyroid hormone. It’s the most common cause of thyrotoxicosis. Causes of hyperthyroidism include Graves’ disease (an autoimmune condition) and overactive thyroid nodules (toxic multinodular goiter).
  • Thyroid inflammation (thyroiditis): Certain bacterial and fungal infections, immune system issues and medications (like lithium and interferons) can cause thyroid inflammation (swelling). The inflammation causes your thyroid to leak stored thyroid hormone, resulting in higher levels of hormones than your body needs. Thyroiditis can also happen after giving birth (postpartum thyroiditis).
  • Excess thyroid medication: Consuming excess thyroid medication (levothyroxine) can cause thyrotoxicosis. This can happen if you have hypothyroidism (underactive thyroid) and take too much of your thyroid medication, whether accidentally or intentionally.
  • Consuming thyroid hormone from food: You can also have too much thyroid hormone in your body by consuming beef that’s contaminated with thyroid tissue from the cow’s neck. This is often called “hamburger thyrotoxicosis,” and it’s a very rare cause of thyrotoxicosis.

What are the risk factors for thyrotoxicosis?

Each cause of thyrotoxicosis has certain risk factors. In general, risk factors for thyrotoxicosis include:

Having access to thyroid medication (levothyroxine) can also be a risk factor for thyrotoxicosis. Someone in your household may accidentally consume it or someone with factitious disorder may take it intentionally.


Diagnosis and Tests

How is thyrotoxicosis diagnosed?

Healthcare providers diagnose thyrotoxicosis if blood tests show that you have elevated thyroid hormone levels and low or undetectable levels of thyroid-stimulating hormone (TSH).

If you have thyrotoxicosis, your provider will also need to figure out what’s causing it, which could lead to another diagnosis. The following tests and assessments can lead to a diagnosis:

  • A physical exam: To start, your provider will do a physical exam to check for signs of thyrotoxicosis, like a rapid heart rate and shakiness (tremor).
  • Thyroid blood tests: Blood tests can check your thyroid hormone levels. When you have thyrotoxicosis, levels of the thyroid hormones triiodothyronine (T3) and thyroxine (T4) are above normal and TSH is lower than normal. Thyroid antibody blood tests can also check if Graves’ disease is the cause.
  • Imaging tests: Various imaging tests of your thyroid can help diagnose the cause of thyrotoxicosis. They include a thyroid ultrasound and a radioactive iodine uptake (RAIU) test and scan. Your provider will go over the options and processes with you and recommend the test they think is best.

Management and Treatment

What is the treatment for thyrotoxicosis?

The treatment for thyrotoxicosis depends on the underlying cause. Your healthcare provider will need to find the cause to recommend the best treatment for you.

Treatment may include:

  • Anti-thyroid medications: Methimazole and propylthiouracil (PTU) block your thyroid from making hormones. These medications can treat many cases of hyperthyroidism.
  • Radioactive iodine (RAI) therapy: RAI therapy destroys overactive thyroid cells. This usually leads to permanent destruction of your thyroid, which then causes hypothyroidism. Because of this, you’ll likely have to take replacement thyroid hormone medication for the rest of your life.
  • Surgery: In some cases, your provider may recommend removing your thyroid gland through surgery (thyroidectomy). This will correct thyrotoxicosis that’s caused by an overactive thyroid gland, but it’ll usually cause long-term hypothyroidism.
  • Beta-blockers: These medications can help manage thyrotoxicosis symptoms — like rapid heartbeat, nervousness and shakiness — in the short term. But they don’t change the level of hormones in your blood.
  • Glucocorticoids (corticosteroids): These medications can help with inflammation and pain if you have thyroiditis.

If outside sources of thyroid hormone are causing thyrotoxicosis — like medications or contaminated beef — thyrotoxicosis should go away once the excess hormones have cleared your system. Your provider may have you do follow-up blood tests to make sure your thyroid hormone levels have returned to a healthy range.

You need treatment for thyroid storm (severe thyrotoxicosis) in a hospital.



Can I prevent thyrotoxicosis?

Most cases of thyrotoxicosis aren’t preventable.

If you’re taking thyroid medication (levothyroxine), you can prevent thyrotoxicosis by never taking more than your healthcare provider prescribes. Taking too much thyroid medication can lead to thyrotoxicosis. It’s also important to store your medication safely away from children and pets.

Outlook / Prognosis

What is the prognosis for people with thyrotoxicosis?

The prognosis (outlook) for people with thyrotoxicosis is generally good if they receive treatment for it. There are several effective forms of treatment for thyrotoxicosis. Just like all treatments, they each have advantages and disadvantages. Together, you and your healthcare provider will determine the best plan for you.

What are the complications of thyrotoxicosis?

Complications from untreated or undertreated thyrotoxicosis include:

These complications most commonly affect people who have untreated hyperthyroidism, especially Graves’ disease.

Thyroid storm can lead to serious complications if you receive delayed or no treatment, including seizures, cardiovascular collapse and death.

Living With

When should I see my healthcare provider for thyrotoxicosis?

If you’re experiencing symptoms of thyrotoxicosis, it’s important to see your healthcare provider so they can figure out the cause and recommend proper treatment.

If you have chronic thyrotoxicosis (usually a form of hyperthyroidism), you should see your provider regularly to make sure your treatment is working well.

What questions should I ask my provider?

If you’ve received a thyrotoxicosis diagnosis, it may be helpful to ask your provider the following questions:

  • What’s causing my case of thyrotoxicosis?
  • What treatment plan do you recommend?
  • What are the pros and cons of my treatment plan for thyrotoxicosis?
  • Can I get thyrotoxicosis again?
  • Am I at risk for thyroid storm?
  • Is this kind of thyrotoxicosis hereditary?

A note from Cleveland Clinic

Although it may sound scary, thyrotoxicosis is a manageable and treatable condition. If you’re experiencing symptoms of thyrotoxicosis — like your bodily functions are going too fast — see your healthcare provider. They can have you undergo some simple tests and recommend treatment to get your body back into balance.

Medically Reviewed

Last reviewed on 06/07/2024.

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