Overactive thyroid

Also known (medically) as hyperthyroidism

An overactive thyroid (hyperthyroidism) is a condition in which the thyroid gland makes too much thyroid hormone. It can cause symptoms such as weight loss, feeling anxious, rapid heartbeat, sleep problems and low energy. Possible treatments include medication, radioactive iodine or surgery.

Possible treatments for overactive thyroid include medication, radioactive iodine or surgery.

The thyroid gland

The thyroid is a small, butterfly-shaped gland in your neck. It produces two thyroid hormones: tri-iodothyronine (T3) and thyroxine (T4). Thyroid hormones help the body use energy, stay warm and keep the brain, heart, muscles, and other organs working as they should.

undefinedIf you have an overactive thyroid you may:

  • lose weight quickly
  • have a fast heartbeat
  • sweat a lot
  • feel nervous and moody. 

Or you may have no symptoms at all; when your doctor is doing a test for another reason, they may discover that you have hyperthyroidism.

Who is affected by overactive thyroid?

  • Thyroid problems are more common in women than men.
  • About 1 in every 8 women develop at least one type of thyroid disorder in their lifetime.
  • Underactive thyroid (hypothyroidism) is the most common followed by overactive thyroid (hyperthyroidism).

What causes overactive thyroid?

Overactive thyroid can be caused by a number of conditions:

  • The most common cause of overactive thyroid is a condition that is passed down in families (hereditary) called Graves' disease. Graves disease is an autoimmune disease in which the body's own immune system affects the thyroid gland causing it to produce too much thyroid hormone.
  • Benign (non-cancer) tumours of the thyroid (called thyroid nodules) or pituitary gland.
  • Too much iodine in the body – can be caused by taking iodine supplements such as kelp or seaweed.
  • Inflammation of the thyroid gland, possibly caused by a virus or problem with the immune system.
  • Some medicines such as lithium or amiodarone can cause an overactive thyroid.

What are the symptoms of hyperthyroidism?

People with an overactive thyroid may have no symptoms at all, or symptoms may start off mild and then progressively get worse. These may include:

  • Losing weight, even though you eat the same or more than usual.
  • Feeling nervous, moody, weak, or tired.
  • Your hands may shake, your heart may beat fast, or you may have problems breathing.
  • Feeling hot and sweaty or have warm, red, itchy skin.
  • Having looser, more frequent, bowel movements than usual.
  • Losing hair, especially fine, soft hair.
  • Having trouble sleeping.

How is overactive thyroid diagnosed?

The diagnosis of hyperthyroidism may not be obvious at first because the symptoms may be mild at the start. If you have symptoms described above, your doctor may carry out tests to help in the diagnosis such as:

  • Cholesterol test: Patients with hyperthyroidism have low cholesterol levels because of an increased metabolic rate.
  • T4 and T3RU (T3 resin uptake) tests: This test is conducted to measure how much thyroid hormones are present in the blood.
  • TSH level test: The hypothalamus produces a hormone known as thyroid stimulation hormone (TSH) which regulates the production of thyroid hormones. Low levels of TSH means thyroid levels are normal or high.
  • Triglyceride level test: People with hyperthyroidism have low levels of triglyceride.
  • Thyroid scan: This gives the physician an idea about whether your thyroid gland is overactive or not. It also provides information if the entire gland or a single area is overactive.
  • Ultrasound: This helps measure the size of the gland and any masses within it. It also provides information about whether the mass is cystic or solid.


How is overactive thyroid treated?

No single treatment is best for all patients with overactive thyroid. The choice of treatment will be influenced by your age, the type of overactive thyroid that you have, the severity of your condition, other medical conditions that may be affecting your health, and your own preference. Your doctor will discuss the treatment options with you. The possible treatments for overactive thyroid are:


  • Beta-blockers such as propranolol or metoprolol. These medicines block the effects of thyroid hormones on the body such as shaking or tremor, and fast heartbeat. These medicines are given for a short time and can help you feel better while you and your doctor decide what your treatment should be.
  • Antithyroid medications such as carbimazole.
  • This helps to reduce the amount of thyroid hormone that is produced by the glands. This works best if your symptoms are mild.

Radioactive iodine therapy

  • This involves taking a drink, or swallowing a capsule, which contains radioactive iodine.
  • This damages the cells that produce the thyroid hormones in the thyroid gland.


  • This involves an operation in which all or part of the thyroid gland is removed.
  • This is often the last resort and is a consideration if all other therapies and medication have not worked. People often consider surgery if they are at a higher risk of experiencing side effects from other treatments.
  • Surgery is a good option if you have a large tumour (called goitre) which causes problems in your neck.

Read more about the treatment of hyperactive thyroid

Possible complications

If hyperthyroidism goes untreated for long durations, it may lead to some severe complications. These include:

  • heart problems
  • eye problems
  • brittle bones
  • thyrotoxic crisis leading to fever, delirium and rapid pulse
  • red skin that may swell up.

When treated, these problems can be avoided.

Learn more

Overactive thyroid NHS Choices UK, 2013
Hyperthyroidism (overactive thyroid gland) HealthInfo Canterbury, 2014
Hyperthyroidism and Pregnancy - patient guide  Endocrine Society and Hormone Health Network, 2015
What does the thyroid gland do? Endocrine Society and Hormone Health Network, 2015
Hyperthyroidism (overactive thyroid) Patient.co.uk, 2012


  1. Campbell K, Doogue M. Evaluating and managing patients with thyrotoxicosis. Australian Family Physician. 2012. 41(8):564-572.
  2. Management of thyroid dysfunction in adultsBPAC, December 2010
Credits: Editorial team.