Overactive thyroid (hyperthyroidism): what are the symptoms and how to treat them

By Cristiano Antonino On Apr 14, 2023

An overactive thyroid, also known as hyperthyroidism or thyrotoxicosis, is where the thyroid gland produces an excessive amount of thyroid hormones

The thyroid gland is a small, butterfly-shaped gland in the neck, just in front of the windpipe.

It produces hormones that affect things like heart rate and body temperature.

Having too much of these hormones can cause unpleasant and potentially serious problems that may require treatment.

An overactive thyroid can affect anyone, but it is about 10 times more common in women than men and usually occurs between the ages of 20 and 40.

Symptoms of hyperthyroidism

An overactive thyroid can cause a wide range of symptoms, including:

nervousness, anxiety and irritability
mood swings
difficulty sleeping
persistent tiredness and weakness
sensitivity to heat
swelling of the neck from an enlarged thyroid gland (goiter)
an irregular and/or unusually fast heart rate (palpitations)
spasms or tremors
weight loss

See a doctor if you have symptoms of an overactive thyroid gland.

They will ask you about your symptoms and if they think you might have a thyroid problem, they can arrange a blood test to check the functioning of your thyroid.

If the blood test shows that you have an overactive thyroid, you may be referred for further tests to identify the cause.

Treatments for an overactive thyroid

An overactive thyroid is generally treatable.

The main treatments are:

medication that prevents the thyroid gland from producing an excessive amount of thyroid hormones
radioiodine treatment – in which a type of radiotherapy is used to destroy thyroid cells, reducing their ability to produce thyroid hormones
surgery to remove part or all of the thyroid so that it no longer produces thyroid hormones

Each of these treatments has advantages and disadvantages.

You will usually see a hormone specialist (endocrinologist) to discuss which treatment is best for you.

Causes of hyperthyroidism

There are several reasons why your thyroid can become overactive.

These include:

Graves’ disease – a condition in which the immune system mistakenly attacks and damages the thyroid gland (about 3 out of 4 people with an overactive thyroid have Graves’ disease)
lumps (nodules) on the thyroid gland – this extra thyroid tissue can produce thyroid hormones, causing levels to be too high
certain medications such as amiodarone, which can be used to treat an irregular heartbeat (arrhythmia)

Additional problems related to hyperthyroidism

An overactive thyroid can sometimes lead to further problems, particularly if it is not treated or well controlled.

These include:

eye problems – such as eye irritation, double vision or bulging eyes
pregnancy complications – such as pre-eclampsia, premature birth or miscarriage
a thyroid storm – a sudden, life-threatening flare-up of symptoms

An overactive thyroid (hyperthyroidism) can cause a wide range of symptoms, although you are unlikely to experience them all.

Hyperthyroidism can also cause the following physical signs

swelling of the neck caused by an enlarged thyroid gland (goiter)
an irregular and/or unusually fast heart rate (palpitations)
spasms or tremors
hot skin and excessive sweating
red palms
loose fingernails
a raised, itchy rash known as urticaria (hives)
patchy or thinning hair
weight loss, often despite an increased appetite
eye problems, such as redness, dryness or vision problems (see complications of an overactive thyroid)

See a doctor if you think you have an overactive thyroid (hyperthyroidism)

A diagnosis will be based on the symptoms and the results of a blood test that evaluates the functioning of the thyroid gland.

Blood test for thyroid function

A family doctor can arrange for a blood test to check thyroid hormone levels.

This is known as a thyroid function test.

The test checks levels of:

thyroid stimulating hormone (TSH) – a hormone produced by the pituitary gland (a gland at the base of the brain) that controls the production of thyroid hormones
triiodothyronine (T3) – one of the main thyroid hormones
thyroxine (T4) – another major thyroid hormone

Your thyroid hormone levels will be compared to what is normal for a healthy person of your age.

A low TSH level and high T3 and/or T4 levels usually mean that you have an overactive thyroid.

Doctors may refer to these measurements as ‘free’ T3 and T4 (FT3 and FT4).

What is considered normal varies depending on things like your age and the exact testing technique used by the lab.

Hyperthyroidism, further tests

If your thyroid hormone levels are high, you may be referred to a specialist for further tests to find out what is causing it.

Further blood tests

You may have another blood test to look for anti-thyroid antibodies.

These are usually found if you have Graves’ disease, a common cause of an overactive thyroid.

A blood test called erythrocyte sedimentation rate (ESR) can also be performed to check for inflammation in the body.

If there are signs of inflammation, the increase in thyroid hormones is caused by thyroiditis (inflammation of the thyroid gland).

Thyroid scan

A thyroid scan can be used to look for problems such as lumps (nodules) on the thyroid gland.

You will be asked to swallow a small amount of a slightly radioactive substance that will be absorbed by your thyroid gland.

It can also be administered by injection.

A scan is then performed to see how much of the substance has been absorbed and to examine the size and shape of the thyroid gland.

An overactive thyroid (hyperthyroidism) is generally treatable

You will usually be referred to a hormone specialist (endocrinologist) who will plan your treatment.

The main treatments are:

medicine
treatment with radioactive iodine
surgery

Medication

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Medicines called thionamides are commonly used to treat an overactive thyroid.

They prevent your thyroid from producing excess hormones.

The main types used are carbimazole and propylthiouracil.

You will usually have to take the medicine for 1 to 2 months before you notice any benefit.

In the meantime, you may also receive another medicine called a beta-blocker to alleviate some of your symptoms.

Once thyroid hormone levels are under control, the dose can be gradually reduced and then stopped.

But some people need to continue taking medication for several years or perhaps a lifetime.

Side effects

During the first two months, some people experience the following side effects

not feeling well
high temperature
headaches
painful joints
altered taste
stomach ache
an itchy rash

These should pass as your body gets used to the medicine.

A less common but more serious side effect is a sudden drop in the number of white blood cells (agranulocytosis), which can make you very vulnerable to infection.

Contact your doctor immediately if you experience symptoms of agranulocytosis, such as high fever, sore throat or a persistent cough.

A blood test may be organised to check the white blood cell count.

Treatment with radioactive iodine

Radioactive iodine treatment is a type of radiotherapy used to destroy the cells of the thyroid gland, reducing the amount of hormones it can produce.

It is a highly effective treatment that can cure an overactive thyroid.

You are given a drink or capsule that contains iodine and a low dose of radiation, which is absorbed by the thyroid gland.

Most people only need one treatment.

It can take several weeks or months before you feel the full benefits, so you may need to take medication, such as carbimazole or propylthiouracil, for a short period.

The radiation dose used during treatment with radioactive iodine is very low, but there are some precautions you will need to take after treatment:

avoid prolonged close contact with children and pregnant women for several days or weeks
women should avoid becoming pregnant for at least 6 months
men should not procreate for at least 4 months

Treatment with radioactive iodine is not suitable for pregnant or breastfeeding women.

It is also not suitable if your overactive thyroid is causing serious eye problems.