An overactive thyroid produces too much thyroid hormone. The condition is also known as hyperthyroidism or thyrotoxicosis.
The thyroid is a small butterfly-shaped gland in the neck, just in front of the windpipe (trachea). It produces hormones that affect things such as your heart rate and body temperature.
Having too much of these hormones can cause serious problems that may need treatment.
An overactive thyroid can affect anyone. It's about 10 times more common in women than men. It usually happens between 20 and 40 years of age.
Symptoms of an overactive thyroid
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 in your neck from an enlarged thyroid gland (goitre)
- an irregular or unusually fast heart rate (palpitations)
- twitching or trembling
- weight loss
When to see your GP
See your GP if you have symptoms of an overactive thyroid.
They'll ask about your symptoms. They can arrange for a blood test to check how well your thyroid is working.
If you have an overactive thyroid, you may be sent for more tests to find out the cause.
Causes of an overactive thyroid
There are several reasons why your thyroid can become overactive.
This is a condition where your immune system mistakenly attacks and damages the thyroid. About 3 in every 4 people with an overactive thyroid have Graves' disease.
Lumps (nodules) on the thyroid
Extra thyroid tissue can produce thyroid hormones, causing your levels to be too high.
Some medicines may cause your thyroid to become overactive. For example, amiodarone, which can be used to treat an irregular heartbeat (arrhythmia).
Treatments for an overactive thyroid
An overactive thyroid is usually treatable.
The main treatments are:
- medicine that stops your thyroid producing too much of the thyroid hormones
- radioiodine treatment – where a type of radiotherapy is used to destroy cells in the thyroid, reducing its ability to produce thyroid hormones
- surgery to remove some or all of your thyroid, so that it no longer produces thyroid hormones
Each of these treatments has benefits and drawbacks. A specialist in hormonal conditions (endocrinologist) will discuss which treatment is best for you.
An overactive thyroid can sometimes lead to further problems.
- 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 and life-threatening flare-up of symptoms
Content supplied by the NHS and adapted for Ireland by the HSE