What Causes An Overactive Thyroid?

Your thyroid may be small, but it plays a critical role in how the rest of your body works. When it isn’t working properly, you may experience unpleasant symptoms, including weight changes, intolerance of hot and cold temperatures, and even different energy levels.

Being aware of the symptoms, causes, and risks of developing a thyroid condition like hyperthyroidism (overactive thyroid) can help you get a diagnosis and treatment sooner rather than later.

So what causes hyperthyroidism, and what symptoms might suggest you have it?

Have you considered clinical trials for Hyperthyroidism?

We make it easy for you to participate in a clinical trial for Hyperthyroidism, and get access to the latest treatments not yet widely available - and be a part of finding a cure.

What does your thyroid do?

Your thyroid is a butterfly-shaped gland in the front of your neck. Its job is to make hormones that help other systems in your body work properly, including your metabolism and heart rate.

When your thyroid produces too many or not enough hormones, other processes in your body may speed up or slow down.

Hyperthyroidism — or overactive thyroid — occurs when your thyroid makes more hormones than your body needs. On the other hand, hypothyroidism (a condition where your thyroid is underactive) occurs when your thyroid doesn’t make enough hormones to sustain your body’s normal processes.

What causes an overactive thyroid?

Many factors can contribute to a hyperthyroidism diagnosis, including:

Graves’ disease

Most people with hyperthyroidism also have Graves’ disease.

Graves’ disease is an autoimmune disorder that causes your immune system to attack your thyroid gland as if it were an invader. This can cause your thyroid to become overactive.


Certain medications can cause your body to produce too many thyroid hormones. Medications containing iodine that are used to treat an irregular heartbeat are an example.

Thyroid nodules

While less common, nodules can grow on your thyroid and cause an increase in hormone production.

Thyroid cancer

In rare cases, thyroid cancer has been known to cause the thyroid gland to produce too many hormones.

What are the symptoms of an overactive thyroid?

Hyperthyroidism can cause various symptoms that differ from person to person.

Common symptoms of an overactive thyroid include:

  • Losing weight unintentionally

  • Increased appetite

  • Sweating and heat intolerance

  • Insomnia

  • Shaky hands

  • Irregular heartbeat

  • Irritability or nervousness

  • More frequent bowel movements

  • Enlarged thyroid (goiter)

Who is at risk of developing an overactive thyroid?

Anyone can develop hyperthyroidism. While it’s often difficult to determine why someone has an overactive thyroid, certain lifestyle factors could increase your chances of developing the condition. These include:

  • Being a woman

  • Being over the age of 60

  • Having a family history of Graves’ disease, other autoimmune disorders, or hyperthyroidism

  • Consuming too much iodine

  • Being pregnant

How is hyperthyroidism diagnosed?

An overactive thyroid must be diagnosed by a healthcare professional even if the condition runs in your family or you recognize the symptoms. You may be diagnosed by your primary care doctor or an endocrinologist.

Your doctor will review your symptoms and medical history. They can also use tests to determine if your thyroid gland is overproducing hormones. Tests for hyperthyroidism include looking at your blood work to check your hormone levels.

With a blood test, your doctor can assess your T3, T4, and thyroid-stimulating hormone (TSH) levels. People with hyperthyroidism have high T3 and T4 levels, while their TSH levels are lower than normal.

You may also have an ultrasound to give the doctor a clear image of your thyroid’s condition.

How is hyperthyroidism treated?

Your doctor or endocrinologist will recommend a treatment plan to help manage your hyperthyroidism and ease your symptoms. Your treatment plan will depend on your condition, medical history, and personal preferences.

Treatment options for hyperthyroidism include:

Anti-thyroid medications

Medications, such as propylthiouracil (PTU) and methimazole (Tapazole), can be used to slow down thyroid hormone production.

In most cases, it can take several months for these medications to work. Hyperthyroidism remission is common, but it’s usually only temporary.

Radioactive iodine treatment

You will be asked to take radioactive iodine by mouth, which will eventually destroy your thyroid cells. This process usually takes three to six months.

Radioactive iodine treatment can cause hypothyroidism that requires life-long thyroid hormone replacement therapy.


Your doctor may recommend removing all or part of your thyroid to control thyroid hormone production.

This is a rare treatment option and is usually reserved for people who are not good candidates for other treatment options, such as pregnant women.

When to a doctor

Hyperthyroidism is a serious condition that can affect your overall health if left untreated. You should schedule an appointment with your doctor if you experience one or more symptoms of an overactive thyroid.

Before your appointment, write down:

  • What your symptoms are, when they started, and how often you experience them

  • Any medications you’re currently taking

  • Your family medical history

  • Any other conditions you may have

  • Any questions you may have about hyperthyroidism and treatment options

The lowdown

Hyperthyroidism (overactive thyroid) occurs when your thyroid gland produces too many hormones. This stops other systems in your body from working properly.

The condition is more common among women over the age of 60 and people with Graves’ disease. Having a family history of autoimmune conditions or consuming excess iodine may also increase your chances of developing hyperthyroidism.

Speak to your doctor if you experience hyperthyroidism symptoms. Your doctor can provide a diagnosis through blood tests and taking an ultrasound of your thyroid.

If you’re diagnosed with an overactive thyroid, you can manage your symptoms with anti-thyroid medication, radioactive iodine, or surgery.

Have you considered clinical trials for Hyperthyroidism?

We make it easy for you to participate in a clinical trial for Hyperthyroidism, and get access to the latest treatments not yet widely available - and be a part of finding a cure.

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