Skip to content

It's our birthday! 20% off all tests* with code 20THBDAY

What is an overactive thyroid?

Understand what an overactive thyroid is and how it can be treated.

What is an overactive thyroid?

An overactive thyroid, also known as hyperthyroidism, is a condition in which your thyroid produces too much of the thyroid hormones (1). 

The thyroid is a small gland positioned in front of your windpipe. It creates hormones that regulate your heartbeat, digestive system and many other bodily functions. The hormones are called triiodothyronine (T3) and thyroxine (T4), and with too much of these, your body overworks itself. 

What causes an overactive thyroid?

An overactive thyroid can occur in both men and women at any age but is more common in women between 20 and 40 years old. Some of the possible causes of hyperthyroidism are: 

  • Graves’ disease – this is a condition in which your immune system attacks and damages the thyroid.
  • Thyroiditis – this is an inflammation of the thyroid gland. 
  • Incorrect medicine dosages – if people overmedicate with thyroid hormone replacement, it can cause hyperthyroidism.
  • Lumps on the thyroid – extra tissue called nodules which grow on the thyroid can lead to an overproduction of thyroid hormones, creating higher levels in the body.

What are the symptoms? 

An overactive thyroid causes an increase in the body’s metabolism, which can cause many symptoms. In some cases, the symptoms are subtle and go unnoticed, but in others, they come on very quickly and severely.

Common symptoms include: 

  • Anxiety and irritability 
  • Mood swings
  • Tiredness
  • Heat sensitivity and sweating
  • Swelling in your neck (goitre)
  • Heart palpitations and arrhythmia 
  • Weight loss
  • Increased appetite 
  • Nausea and loose bowels

How is hyperthyroidism diagnosed?

Doctors can diagnose this condition with a short physical examination or blood tests. 

Your doctor will talk to you about any symptoms you are having, and in some cases, may perform an ultrasound scan of your thyroid gland. 

A blood test is a very accurate method of diagnosing an overactive thyroid. In most people with this condition, this will show low levels of the thyroid-stimulating hormone (TSH) and high levels of thyroxine (T4). If you are diagnosed with hyperthyroidism, another blood test is used to measure your TSH receptor antibodies to establish whether it is being caused by Graves’ disease (2). A cholesterol test may also be useful because low cholesterol levels can indicate an elevated metabolic rate.

Check out Medichecks’ range of thyroid tests or read our thyroid guide if you need help choosing which test is most suitable for you.

How can it be treated?

An overactive thyroid is treatable; your doctor’s approach will depend on which type of hyperthyroidism you have and how severe it is. Some treatments are:

  • Beta-blockers – this medication is prescribed to treat very mild cases of hyperthyroidism as it helps to relieve some of the symptoms.
  • Medication – antithyroid medicines are usually the first response to hyperthyroidism, particularly for children and pregnant women. They are used to stop your thyroid producing high levels of hormones. The tablets should be taken daily and only stopped if advised to do so by a doctor.
  • Radioiodine – radiotherapy is used to destroy cells in the thyroid, which reduces its ability to produce thyroid hormones. Radioiodine is very effective, safe and has minimal side-effects.
  • Surgery – your thyroid gland can be partially or entirely removed during an operation. This option is usually considered if medication does not work or if your thyroid gland is swollen. After surgery, you will need to take levothyroxine for the rest of your life (3).

A balanced diet, along with a few specific foods, can support thyroid health. Hyperthyroidism can cause your bones to weaken, so having sufficient amounts of calcium is beneficial. You can find calcium in foods such as cheese, yoghurt, spinach, soybeans, and nuts (especially almonds). Taking vitamin D and calcium supplements during treatment can strengthen your bones (4).

Visit our blog for a comprehensive overview of the thyroid diet or speak to a doctor or dietitian about the best dietary choices for you. 

What are the health risks of hyperthyroidism?

An overactive thyroid can cause complications if it is not treated appropriately or early enough. Some of the related health risks are: 

  • Eye problems – the body’s immune system can attack the tissues around the eyes and cause issues such as irritation, double vision and bulging eyes.
  • Heart problems – the heart can develop an irregular rhythm and struggle to pump efficiently if hyperthyroidism is not treated.
  • Mental health problems – hyperthyroidism can cause anxiety and hyperactivity.
  • Weight loss and loss of bone – the increase in metabolic rate increases the energy requirements of the body, which responds by using energy stored in body fat. The calcium stored in bones can also decrease, resulting in osteoporosis.
  • Pregnancy complications – untreated hyperthyroidism can cause preeclampsia, premature birth and miscarriage. 
  • A thyroid storm – this is the term given to a sudden and life-threatening flare-up of symptoms (5).

If you are planning a pregnancy and have an overactive thyroid, it is important to check that your hormone levels are normal. As soon as you are pregnant, you should have a thyroid function test. Your doctor will likely adjust your medication and recommend more frequent blood tests. 

What next?

If you have any concerns or are experiencing any symptoms related to an overactive thyroid, visit your doctor. Medichecks also provides a range of thyroid tests and guides for further support and information. 


1.    NHS (2019). Overactive thyroid (hyperthyroidism). [online] Available at: [Accessed: 02/03/20].

2.    British Thyroid Foundation (2018). Hyperthyroidism. [online] Available at: [Accessed 02/03/20].

3.    British Thyroid Foundation (2018). Hyperthyroidism. [online] Available at: [Accessed 02/03/20].

4.    Lights, V. Solan, M. and Fantauzzo, M. (2016). Hyperthyroidism. [online] Healthline. Available at: [Accessed 02/ 03/20].

5.    NHS (2019). Overactive thyroid (hyperthyroidism). [online] Available at: [Accessed: 02/03/20].