HealthInfo Waitaha Canterbury
Overactive thyroid (hyperthyroidism)
Repe tenga hoehe rawa
Your thyroid is a small, butterfly‑shaped gland in your neck. It produces two thyroid hormones, tri‑iodothyronine (T3) and thyroxine (T4).
Thyroid hormones help your body use energy and stay warm. They keep your brain, heart, muscles and other organs working as they should.
An overactive thyroid (hyperthyroidism) happens when your thyroid gland makes too much of these hormones. This causes your body's metabolism to speed up, which in turn can cause symptoms.
An overactive thyroid is more common in women than men and can occur at any age.
There are several causes for an overactive thyroid. Treatments include tablets, radioactive iodine and surgery.
Symptoms of an overactive thyroid
Symptoms of an overactive thyroid include:
- feeling nervous or anxious
- shaking
- sweating more than usual
- have a racing heartbeat or palpitations
- losing weight even though you have a good appetite
- tiredness and muscle weakness
- a swollen thyroid gland (called a goitre).
You may also get problems with your eyes, have difficulty sleeping and diarrhoea. If you're a woman, you may notice that your periods become lighter.
If left untreated for a long time, you can develop thin bones (osteoporosis).
Causes of an overactive thyroid
Grave's disease is the commonest cause of an overactive thyroid. This is an autoimmune disease.
Your immune system usually fights off infections but when you have an autoimmune disease, your immune system attacks your own cells. Your body makes a tiny protein (antibody) that attaches to your thyroid, causing it to make too much thyroid hormone. We do not know what triggers this, but it sometimes runs in families.
Thyroid nodules (lumps) can also produce too much thyroid hormone. There can be a single nodule or several, which is known as multinodular goitre (enlarged thyroid).
Rarer causes include an inflammation of the thyroid known as thyroiditis and some medicines, such as lithium or amiodarone.
Diagnosing an overactive thyroid
A blood test measures your thyroid hormones and TSH (thyroid stimulating hormone). TSH is a hormone that controls how much thyroxine you make. It's made by your pituitary gland at the base of your brain. If your thyroid is already making too much thyroxine, your TSH will be low.
A blood test can diagnose Graves’ disease by showing thyroid antibodies. If the blood test doesn't show antibodies, you may need a radionuclide thyroid scan to determine the underlying cause of your thyroid overactivity.
HealthInfo recommends the following videos
- Alila Medical Media – Thyroid gland, hormone and thyroid problems animation
A four‑minute video about the thyroid gland, hyperthyroidism (overactive thyroid) and hypothyroidism (underactive thyroid).
HealthInfo recommends the following pages
- American Thyroid Association – Hyperthyroidism (overactive thyroid)
Answers to commonly asked questions about hyperthyroidism.
- Patient.info – Hyperthyroidism (overactive thyroid)
Information about the causes and treatment of an overactive thyroid.
On the next page: Treating an overactive thyroid (hyperthyroidism)
Written by HealthInfo clinical advisers. Last reviewed July 2023.
Sources
Review key: HITHY-49064
