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Written by Ada’s Medical Knowledge Team

Updated on

What is hyperthyroidism?

Hyperthyroidism is a condition where the thyroid gland is overactive, or hyperactive, and causes an excess of thyroid hormone in the body. The thyroid is a small, butterfly-shaped gland in the lower part of the neck, below the voice box. Hormones released by the thyroid regulate the body’s metabolism, affecting functions such as heart rate, digestion and temperature. 1 2

Having too much thyroid hormone, a state which is called thyrotoxicosis, can cause symptoms like difficulty sleeping, nervousness, rapid heartbeat, intolerance to heat and weight loss despite a healthy appetite. 1 2 Hyperthyroidism can affect anyone, of any age, though it seems to be more prevalent among women and older adults. It is not a very common condition. 3 Hypothyroidism, a condition in which the thyroid is underactive and causes a lack of thyroid hormone, is more common. 4 Sometimes, a period of hyperthyroidism can occur as part of thyroiditis, inflammation of the thyroid gland, and follow or be followed by hypothyroidism. If you think that you might have a thyroid condition, you can try using the Ada app to find out more about your symptoms.

Hyperthyroidism may have a number of different causes. The most common is Graves' disease, also known as diffuse toxic goiter or Basedow’s disease, an autoimmune disorder in which the immune system mistakenly stimulates the thyroid to produce too much thyroid hormone. Other causes of hyperthyroidism include thyroiditis, thyroid nodules and, rarely, certain medications and tumors. 1 2 3

If left untreated for a long period of time, hyperthyroidism can lead to serious complications, including heart problems. 5 However, hyperthyroidism is relatively easy to diagnose with blood tests, and effective treatment options are available. These include medication, radioactive iodine therapy and, in some cases, surgery. 1 2 3

Signs and symptoms of hyperthyroidism

Symptoms of excess thyroid hormone may include: 1 2 3 6 7 8 9 10

Psychological symptoms

  • Anxiety or nervousness; some people may present with signs of depression
  • Irritability or agitation
  • Insomnia (sleep disturbances)

Physical symptoms


  • Increased sweating
  • Intolerance of heat, e.g. hot weather
  • Fatigue, i.e. generally feeling tired or weak
  • Tremors (shaky hands)
  • Feeling of weakness in the muscles, particularly in the upper arms and thighs
  • Difficulty exercising
  • Swelling of the thyroid gland (goiter)


  • Racing heart or palpitations, i.e. pronounced awareness of one’s heartbeat
  • High blood pressure
  • Shortness of breath

Digestive system

  • Weight loss or difficulty gaining weight, in spite of a good or even increased appetite
  • Increased frequency of bowel movements
  • Nausea and vomiting

Skin, hair and eyes

  • Itchy skin
  • Thinning of the hair
  • Eye bulging and irritation (Graves' ophthalmopathy, or thyroid eye disease)
  • Rarely, reddening and thickening of the skin, most often on the shins or tops of the feet (Graves’ dermopathy or pretibial myxedema) 11

Reproductive symptoms

Though not common, some people may experience weight gain due to increased appetite in hyperthyroidism. Some people may find that their appetite decreases. If you think that you may have signs of hyperthyroidism, you can try using the Ada app for a free assessment.

Hyperthyroidism causes

Hyperthyroidism has a number of possible causes, including the following: 1 2 3 5 10

Graves' disease

Also called Basedow’s disease or diffuse toxic goiter, this is the most common cause of hyperthyroidism. It is an autoimmune condition in which the immune system mistakenly stimulates the thyroid gland to produce excess thyroid hormone. Graves' disease often runs in families and mainly affects young adult women, though it can occur in anyone, of any age.

Thyroid nodules

A thyroid nodule is a small lump that develops in the thyroid gland. Sometimes, thyroid nodules cause the production of too much thyroid hormone; these are termed hot or toxic nodules. A single nodule is called toxic solitary adenoma and is typically found in people between 30 and 50 years of age.

If several nodules are present, it is called toxic multinodular goiter or Plummer disease – this is most commonly found in older adults. Nodules are made up of abnormal thyroid tissue, but they are not usually cancerous.


Transient hyperthyroidism can also develop as a result of inflammation of the thyroid gland (thyroiditis), which may be part of various disorders, including De Quervain’s thyroiditis, Hashimoto’s thyroiditis, silent thyroiditis and postpartum thyroiditis.

Read more about Thyroiditis »


Though unusual, hyperthyroidism can also be caused by certain medications, including amiodarone and lithium. Taking too many iodine supplements or over-the-counter formulations that contain thyroid hormones can also lead to hyperthyroidism in some cases.

If a person is taking levothyroxine for hypothyroidism, and the dose is too high, this too can cause symptoms of hyperthyroidism.

Other causes

A very small number of pregnant women may develop hyperthyroidism from hyperemesis gravidarum – a condition that causes severe nausea and vomiting during the first few months of pregnancy]. 12

Hyperthyroidism can also be caused by cancer in the thyroid gland or certain types of tumors. It can also occur, for a short period of time, after exposure to radiation, for example following treatment with radioiodine or radiotherapy.

Diagnosis of hyperthyroidism

After taking the person’s medical history and performing a physical examination, a doctor will typically order blood tests to check thyroid hormone levels.

Blood tests for hyperthyroidism

These tests typically measure: 13

  • TSH (thyroid stimulating hormone)
  • FT4 (free thyroxine)
  • FT3 (free triiodothyronine) – only occasionally

TSH levels vary according to the amount of T4 (thyroxine) that is needed. T4 is converted into T3 (triiodothyronine), the biologically active form of thyroid hormone. In hyperthyroidism, where there is an excess of thyroxine in the body, the level of TSH is usually low and the FT4 and FT3 high. 1 14

If blood tests show normal levels of FT4 and FT3, but low TSH, a diagnosis of subclinical hyperthyroidism may be made and follow-up tests ordered for approximately two months’ time. In some cases, treatment may be recommended for persistent subclinical hyperthyroidism, particularly in older adults, as the condition may lead to complications. 10

If the doctor suspects that Graves' disease may be present, they will usually also order blood tests to check for thyroid antibodies that are often seen in the disorder. If another cause is suspected, further blood tests may be necessary. 3 13

Imaging tests

In some cases, an ultrasound scan of the thyroid or a radioactive iodine uptake test with or without a procedure called a thyroid scan, may be recommended to confirm the diagnosis and cause of hyperthyroidism. 3 These imaging tests can detect thyroid nodules and inflammation, and provide insight into how the thyroid gland is functioning.

Thyroid ultrasound

This is a quick and simple scan that uses sound waves to create an image of the thyroid gland. No radioactive substances are involved. 15

Radioactive iodine uptake test and thyroid scan

These tests require the administering of a small amount of a weak radioactive substance, which temporarily collects in the thyroid. Imaging is performed a number of hours later, either using a device called a gamma probe, or a radioactive iodine tracer in the case of a thyroid scan procedure. 16 17 18 19

Differential diagnosis

A doctor will need to rule out other conditions that can cause some of the same symptoms as hyperthyroidism, such as anxiety and panic disorder, diabetes, heart disease and drug abuse. 1

Hyperthyroidism treatment

If a person is diagnosed with hyperthyroidism they will usually be referred to an endocrinologist, a doctor specializing in the body’s hormones and hormonal conditions, for treatment. 10 The aims of treatment are to bring the levels of thyroid hormone into the acceptable range and manage any complications that may have arisen as a result of hyperthyroidism. 3

There are a number of different treatment options. When advising which is most appropriate for a particular person, their age, general health, personal preferences and the cause of hyperthyroidism will be taken into account by the doctor. Treatment may include the following: 1 2 3 10 14

Antithyroid medication

A doctor may prescribe antithyroid medication to reduce the production of thyroid hormone. This is typically methimazole or carbimazole, or propylthiouracil if a person is in their first trimester of pregnancy. It may take a few weeks for thyroid hormone levels to stabilize, during which time beta-blockers or calcium-channel blockers may be recommended to alleviate hyperthyroidism symptoms like anxiety, palpitations and tremors.

The medication typically needs to be taken every day for a year to a year and a half. In some cases, it may then be possible to stop taking the antithyroid medication. However, some people will need to stay on it for life or consider another long-term treatment option.

A doctor will be able to advise on how long to take antithyroid medication, as well as precautions that need to be taken while on it. Antithyroid medication is typically not recommended for cases of transient hyperthyroidism caused by thyroiditis, as these tend to resolve on their own.

Radioiodine therapy

In many cases of hyperthyroidism, radioactive iodine (radioiodine) therapy, also known as radioactive iodine ablation, may be recommended. A medical specialist will administer a single dose of radioactive iodine, typically in the form of a capsule or liquid. This iodine accumulates in the thyroid, gradually destroying thyroid tissue and decreasing the production of thyroid hormone. It may take a few months to see results.

If the therapy results in a complete, permanent lack of thyroid hormone production, which is often a desired outcome in the treatment of Graves' disease, it will be necessary to take synthetic thyroid hormone, levothyroxine, daily, to prevent the development of hypothyroidism. This is known as block-and-replace treatment.

It may be necessary to undergo short-term treatment with antithyroid medication prior to radioiodine therapy, particularly where symptoms are severe, the person is older or they have a heart condition. This treatment is typically stopped approximately a week before the radioiodine therapy is performed. Another short course of medication may be necessary after the procedure.

Radioiodine therapy is generally considered to be a safe and effective procedure that does not cause problems in the body. As a precaution, however, it is recommended that the person avoid prolonged close contact with others for a while after the treatment.

Women who are pregnant or breastfeeding, people with severe Graves' ophthalmopathy and children under five years of age are not eligible for radioiodine therapy. Anyone planning to have a child is advised to wait for a certain period of time before trying to conceive afterwards. A doctor will be able to explain all necessary precautions in detail.

Thyroid surgery (thyroidectomy)

In some cases, doctors may recommend an operation to remove part or all of the thyroid gland (thyroidectomy). However, this is usually reserved for cases of hyperthyroidism where other types of treatment have been unsuccessful or intolerable, or a very large goiter (swelling of the gland) is causing problems, such as difficulty breathing.

A thyroidectomy is considered to be effective and safe. However, as with any type of surgery, there is a small risk of complications. Before having surgery, a person will typically be prescribed a course of antithyroid medication to minimize the risk of complications like thyroid storm (see below).

Depending on the amount of tissue that is removed, it will often be necessary to take synthetic thyroid hormone, levothyroxine, daily, to prevent the development of hypothyroidism.

Long-term management

Regardless of the type of treatment a person receives, they will need to go for regular checkups afterwards. These will typically include blood tests to check that thyroid hormone levels are within range.

People with Graves' disease may experience periods of remission and relapse of hyperthyroidism. It is important to monitor for symptoms of hyperthyroidism, as well as hypothyroidism, such as sensitivity to cold, dry skin, fatigue and unexplained weight gain, and consult a doctor should any develop.

Natural remedies for hyperthyroidism

While a number of over-the-counter products may claim to treat hyperthyroidism, there are currently no recognized natural remedies for the condition. If a person has symptoms of hyperthyroidism, it is important that they consult a medical doctor without delay.

Complications of hyperthyroidism

If left untreated, or inadequately treated, hyperthyroidism can lead to a number of complications. These include: 1 3 10 20

Thyroid eye disease

A small number of people with hyperthyroidism develop related eye problems, termed thyroid eye disease. Because this is most commonly associated with Graves' disease, it is often called Graves' ophthalmopathy.

The eyes become inflamed and swollen, leading to pain and discomfort, and vision may be affected. Thyroid eye disease ranges from mild to severe, with treatment correspondingly differing from eye drops to medication and surgery. A person with thyroid eye disease will typically be referred to an eye specialist (ophthalmologist) for optimal management of the condition. 21 22

Thyroid storm

Rarely, a person with hyperthyroidism may develop a life-threatening condition, known as thyroid storm or thyrotoxic crisis. During thyroid storm, thyroid hormone levels become extremely high, resulting in a medical emergency.

Signs and symptoms of thyroid storm include:

  • Significantly elevated temperature
  • Profuse sweating
  • Very fast heartbeat
  • High blood pressure
  • Severe nausea
  • Vomiting
  • Diarrhea
  • Severe mental agitation and anxiety
  • Delirium or psychosis
  • Seizures

The person may develop atrial fibrillation (abnormal heart rhythm) and heart failure or enter a comatose state.

While there is sometimes no obvious trigger, thyroid storm is more likely to develop after the discontinuation of antithyroid medication, treatment with radioiodine, a severe infection or surgery.

A person experiencing thyroid storm requires urgent hospital care, which typically includes an intravenous drip, beta-blockers, antithyroid medication and other treatments.

Other complications

A person may also develop the following as a result of hyperthyroidism:

  • Increased risk of heart problems, such as atrial fibrillation and heart failure
  • Increased risk of bone weakness, also known as osteoporosis
  • Increased risk of complications during pregnancy, such as miscarriage

With effective medical management of hyperthyroidism, the risk of complications is minimized.

Hyperthyroidism and pregnancy

Hyperthyroidism is not common in pregnancy. However, if it does occur and is not managed properly, the condition can cause serious complications for both mother and baby. 23

Hyperthyroidism and children

Hyperthyroidism can affect people of any age, though it is less common in children than adults. Most cases of hyperthyroidism in children are caused by Graves’ disease, and it is more prevalent among girls than boys. 10 24

Symptoms of hyperthyroidism in children may develop slowly, but typically include unexplained weight loss, fatigue, behavioral changes and intolerance of hot conditions. If left untreated, hyperthyroidism can affect a child’s growth and development. 10 24

Treatment options are largely the same as for adults, though antithyroid medication is preferred. 10 14

Neonatal hyperthyroidism

A very small number of newborn babies may present with hyperthyroidism, typically where the mother has Graves' disease. Symptoms of hyperthyroidism in infants may include irritability, restlessness, rapid heartbeat, lack of weight gain and goiter.

The hyperthyroidism usually clears up within a few months, but it may be necessary for the baby to be treated with antithyroid medication in the interim, to avoid complications. 1 10

Other names for hyperthyroidism

  • Overactive thyroid
  • Thyrotoxicosis

Hyperthyroidism FAQs

Q: Hyperthyroidism vs. hypothyroidism – what is the difference?
A: Hyperthyroidism is a condition where the thyroid gland is overactive, causing an excess of thyroid hormone in the body. Symptoms may include increased heart rate, weight loss and anxiety. Hypothyroidism is a condition where the thyroid gland is underactive, causing a deficiency of thyroid hormone in the body. Symptoms may include tiredness, weight gain and depression.

Read more about Hypothyroidism »

Q: What is the best diet for hyperthyroidism?
A: No specific diet is recommended for people with hyperthyroidism. Generally speaking, a balanced, healthy diet is considered to be sufficient. It is not advisable to adopt a special diet or take nutritional supplements without first consulting a doctor. It is especially important that kelp and iodine supplements be avoided unless recommended by a doctor, as they can worsen hyperthyroidism. 25

Q: Can hyperthyroidism cause weight gain?
A: While weight loss is more common in hyperthyroidism, some people may experience weight gain. This may occur if they eat significantly more than usual due to increased appetite. 6

Q: What are the symptoms of hyperthyroidism in men?
A: Symptoms of hyperthyroidism in men include anxiety, irritability, increased sweating, tremors, tiredness and other symptoms detailed above.