Overactive thyroid

What is an overactive thyroid?

Your thyroid is a small gland that’s shaped like a butterfly and is found at the front of your neck just below the larynx. When your thyroid is overactive, it produces excess levels of the two thyroid hormones, thyroxine (T4) and/or triiodothyronine (T3).

If you have an overactive thyroid, you may develop symptoms like weight loss, diarrhoea, anxiety or eye problems. 

What are the symptoms of an overactive thyroid?

The symptoms of an overactive thyroid can be very generalised and difficult to differentiate from other conditions. Some common symptoms include: 

• Weight loss 

• Diarrhoea 

• Poor heat tolerance and profuse sweating

• Fatigue 

• Anxiety, insomnia or being irritable

• Mood swings 

• Muscle weakness 

• Loss of libido (sex drive) 

• Persistent thirst

• Shorter or missed periods in women

As well as the above symptoms, look out for these physical signs of an overactive thyroid: 

• Eye changes

• Swelling in your neck

• Red palms 

• A tremor 

• Heart palpitations 

What causes an overactive thyroid?

There are a number of conditions that can result in your thyroid producing excessive amounts of hormone. The most common include:    

• Grave’s disease – an autoimmune condition

• Thyroid nodules – lumps containing thyroid tissue can develop on the thyroid gland and produce thyroid hormones 

• Thyroiditis – inflammation of the thyroid

• Medication – iodine-containing medicines such as amiodarone

Less common causes of an overactive thyroid include thyroid cancer, a pituitary adenoma or atypical pregnancies (such as multiple pregnancies).

An overactive thyroid in pregnancy

Pregnancy can sometimes be a trigger for the production of excess thyroid hormones. It’s important that this is controlled to prevent the risk of preeclampsia, miscarriage, premature labour and birth and low birthweight. 

Hyperthyroidism in pregnancy will be managed by a specialist as treatment can be complicated. 

How to test for an overactive thyroid

You should speak to a GP if you think you have symptoms of an overactive thyroid. Your GP will ask about the symptoms and request a blood test to look at your  thyroid function (TFT) if needed. 

These examples below may mean you have or are at risk of developing hypothyroidism.

• Low TSH and high T4 and/or T3 – could mean you have an overactive thyroid  

• Low TSH but normal T4 and T3 – may mean you are at risk of developing an overactive thyroid in the future. This is often referred to as ‘subclinical hyperthyroidism’.

Treatments for hyperthyroidism

The options for managing hyperthyroidism include:

• Medications – carbimazole or propylthiouracil are used to reduce the hormone levels and beta blockers can help with symptoms

• Radioactive iodine therapy – a form of radiotherapy that can help prevent excess production of hormones

• Surgery – sometimes surgical removal of the thyroid gland is recommended 

Typically, if your hyperthyroidism is treated then you can live a relatively normal life. But if left untreated, complications such as thyroid eye disease can develop.

If you think you’re experiencing symptoms of an overactive thyroid it is important you see a doctor.