Hyperthyroidism: Signs, Causes, and Treatments

Medically Reviewed By Kelly Wood, MD
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Hyperthyroidism occurs when you have an overactive thyroid gland. In other words, it happens when the thyroid gland produces too much thyroid hormone. This speeds up metabolism and can affect many organs. Common hyperthyroidism symptoms may include anxiety, nervousness, fatigue, weight loss, hand tremors, and an irregular heartbeat.

A variety of factors and conditions can cause hyperthyroidism. Prompt diagnosis and treatment can help prevent serious lifelong complications.

This article provides a detailed look at hyperthyroidism, including its symptoms, how doctors diagnose causes of hyperthyroidism, and some treatment options for hyperthyroidism. 

What is hyperthyroidism?

Goiter can be due to benign or cancerous causes. Drahreg01, CC BY-SA 3.0, via Wikimedia Commons

Hyperthyroidism is also known as an overactive thyroid. The thyroid gland is located in the front of the neck. It produces thyroid hormone, which is a hormone necessary for typical metabolism.

In hyperthyroidism, the thyroid produces too much thyroid hormone. This leads to an overactive metabolism. Common hyperthyroidism symptoms include anxiety, nervousness, weight loss, and high blood pressure.

Hyperthyroidism can result from various factors, including inflammation of or a growth on the thyroid gland. Graves’ disease, which is an autoimmune condition, is the most common cause of hyperthyroidism. Other causes include thyroid nodules, iodine exposure, and high levels of thyroid-stimulating hormone (TSH) from the pituitary gland. 

Prompt diagnosis and treatment can lead to a good outlook. In some cases, it may also lead to curing the condition. With regular medical care and compliance with their treatment plan, many people with the condition live active, regular lives.

In some cases, however, hyperthyroidism can lead to serious, potentially life threatening symptoms and complications. These include heart arrhythmias and heart failure. Seek immediate medical care (call 911) for serious symptoms, such as chest pain, heart palpitations, or shortness of breath

What are the symptoms of hyperthyroidism?

Hyperthyroidism symptoms are the result of an overactive metabolism.

Common symptoms include:

What causes hyperthyroidism?

Hyperthyroidism occurs when the thyroid gland is overactive and produces too much thyroid hormone. A variety of conditions can stimulate the thyroid gland to make too much thyroid hormone.

Some causes of hyperthyroidism include:

  • Autoimmune thyroid disease: This is also known as Graves’ disease, and it occurs when the immune system makes atypical autoantibodies that attach to thyroid gland cells and stimulate them to secrete excess thyroid hormone. This is the most common cause of hyperthyroidism.
  • Excess levels of TSH: This occurs when the pituitary gland produces too much TSH
  • Iodine exposure: The thyroid uses iodine to produce thyroid hormone. Consuming too much iodine can cause hyperthyroidism.
  • Overactive thyroid nodule: This noncancerous cyst grows on the thyroid gland and produces additional thyroid hormone. This more commonly affects older adults.
  • Thyroiditis: This refers to inflammation of the thyroid gland due to a viral infection. It may also develop after giving birth (postpartum thyroiditis).
  • High dosages of thyroid hormone medications: If you are taking thyroid hormone medications for hypothyroidism, you should have your thyroid hormone levels checked at least once per year to determine if the dosage needs adjusting. Some medications can interact with thyroid hormone medications, so it is important to check with your doctor about all medications and supplements you take.

Hyperthyroidism vs. hypothyroidism

The thyroid gland can become overactive or underactive. An underactive thyroid makes less thyroid hormone than the body requires. This is called hypothyroidism. 

Like hyperthyroidism, the most common cause of hypothyroidism is an autoimmune condition. However, with autoimmune hypothyroidism (Hashimoto’s thyroiditis), the body makes antibodies that attack the thyroid gland. This causes inflammation that disrupts the ability of the thyroid gland to make hormones. 

What are the different types of hyperthyroidism? 

There are several types of hyperthyroidism. The sections below look at these in more detail.

Primary hyperthyroidism

Primary hyperthyroidism occurs when elevated thyroid hormone levels are directly traceable to the thyroid gland itself. Examples include inflammation of the thyroid gland and a growth on the thyroid gland. 

Secondary hyperthyroidism

Secondary hyperthyroidism occurs when the problem is not with the thyroid gland. Instead, the issue lies elsewhere — usually in the pituitary gland or hypothalamus.

The pituitary gland is the master gland of the endocrine system. It releases hormones that control other glands and organs. This includes the thyroid gland. The pituitary gland senses when thyroid hormone levels are too high or too low. When levels are too low, it releases TSH. TSH prompts the thyroid gland to make thyroid hormone. When the pituitary gland does not make enough TSH, secondary hyperthyroidism can develop.

Noncancerous tumors of the pituitary gland can also make it overactive and lead to hyperthyroidism.

Secondary hyperthyroidism may also occur if the hypothalamus gland does not produce enough thyrotropin-releasing hormone.

Subclinical vs. overt hyperthyroidism

Subclinical hyperthyroidism means that you have low or undetectable TSH with normal free thyroxine (T3) and total or free triiodothyronine (T4) levels.

Overt hyperthyroidism is defined by low or undetectable TSH with high free T3 or high free T4 levels.

What are the risk factors for hyperthyroidism?

Females are more likely than males to develop hyperthyroidism. However, several other factors increase the risk of developing the condition. Not all people who are at risk of hyperthyroidism will develop it.

Risk factors include:

  • being assigned female at birth
  • being 40 years or younger or 60 years or older
  • having certain common viral infections
  • receiving particular drug treatments, such as certain cancer and AIDS therapies
  • having a family history of thyroid disease, including Graves’ disease
  • having a history of autoimmune conditions
  • having iodine exposure, including from foods containing iodine and some heart medications
  • having a recent pregnancy
  • taking too high a dosage of thyroid replacement hormone
  • sustaining trauma or an injury to the thyroid
  • having other health conditions, including:

How do you prevent hyperthyroidism? 

In general, it is not possible to prevent hyperthyroidism. Most of the risk factors and causes are not avoidable. 

If you take thyroid replacement hormone for an underactive thyroid, regular monitoring will help keep your levels in the appropriate range. 

If you have risk factors for hyperthyroidism, talk with your doctor about how to recognize early symptoms.

How do doctors diagnose hyperthyroidism?

To diagnose hyperthyroidism, your doctor will take a medical history, perform an exam, and order thyroid tests. 

During the exam, your doctor will feel the thyroid gland in your neck. They may also test your reflexes, check your pulse, and examine your eyes and skin. You may also need to extend your arms and hands so that your doctor can see if your hands are steady.

Tests to diagnose thyroid disease, including hyperthyroidism, include:

  • Blood tests: These tests measure the amount of TSH, T4, T3, and thyroid antibodies.
  • Thyroid scan: This imaging exam uses a radioactive injection to check how much iodine your thyroid absorbs. This highlights nonfunctioning areas of the thyroid gland. This is also known as a radioiodine uptake test.
  • Thyroid ultrasound: This imaging exam looks for thyroid nodules without using radiation.

Your doctor may also ask you several questions about your symptoms, medical history, and any medications you take. These questions may include: 

  • What symptoms are you experiencing?
  • When did your symptoms begin?
  • Are your symptoms constant, or do they come and go?
  • What, if anything, seems to make your symptoms better or worse?
  • Do you have a family history of thyroid disease?
  • What other medical conditions do you have?
  • What medications do you take?
  • Have you recently been pregnant or given birth?

How do you treat hyperthyroidism?

Prompt diagnosis and treatment of an overactive thyroid can return thyroid hormone to appropriate levels. Treating hyperthyroidism is important to relieve symptoms and prevent health problems.

Doctors recommend treatments depending on how severe your symptoms are and what is causing your hyperthyroidism. 

Hyperthyroidism treatment includes:

  • Beta-blockers: These drugs can minimize some of the symptoms, such as a rapid heart rate and anxiety.
  • Antithyroid or hyperthyroidism medication: This type of therapy decreases the overproduction of thyroid hormone. In some cases, antithyroid medications may even cure hyperthyroidism.
  • Thyroid surgery: This procedure removes part or most of the overactive thyroid gland. If a surgeon removes part of the thyroid, thyroid hormone levels may return to normal, curing the condition. If they remove the entire thyroid, it results in an underactive thyroid, and you will need lifelong thyroid hormone replacement.
  • Radioactive iodine: Swallowing radioactive iodine can reduce overactivity and overproduction of thyroid hormone. This treatment can also result in underactive thyroid and the need for lifelong thyroid hormone replacement. It may also lead to normalized thyroid hormone levels.
  • Hypothyroidism medication adjustments: This involves testing levels of thyroid hormone in the blood and lowering the dosage of thyroid hormone medications used to treat hypothyroidism.

How does hyperthyroidism affect quality of life? 

The thyroid gland influences just about every bodily function. When there is a problem with this gland, your whole body can feel the effects. You may experience reductions in physical, mental, and emotional well-being. 

All of this can contribute to decreases in quality of life (QoL). Eye symptoms, fatigue, depression, and anxiety can all contribute to decreased QoL in hyperthyroidism. 

Researchers have studied the effect that treatments have on improving QoL for people with Graves’ hypothyroidism. They compared people who received radioiodine therapy with those who underwent surgery (thyroidectomy) and took antithyroid drugs.

Around 6–10 years later, people with Graves’ hypothyroidism had lower QoL regardless of treatment compared with people in general. People who received radioiodine treatment reported worse thyroid-related QoL than people who underwent surgery and took antithyroid drugs.  

If you are considering treatment options, talk with your doctor about QoL issues. Be sure to ask about the latest research in this area and what you can expect with treatment.

What are the potential complications of hyperthyroidism?

Complications of untreated hyperthyroidism can be serious. Some can even be life threatening. You can help reduce the risk of serious complications by following your treatment plan. 

Complications of untreated hyperthyroidism include:


Hyperthyroidism occurs when the thyroid gland overproduces thyroid hormone. This can speed up metabolism and cause many body-wide symptoms, including feeling nervous and fatigued and having hand tremors and an irregular heartbeat. A variety of factors can cause hyperthyroidism. 

Prompt diagnosis and treatment of hyperthyroidism can return thyroid hormone to appropriate levels, relieve the symptoms, and prevent long-term health problems. 

With regular medical care and compliance with their treatment plan, many people with this condition live active, healthy lives.

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Medical Reviewer: Kelly Wood, MD
Last Review Date: 2022 Feb 3
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