Skip Ribbon Commands
Skip to main content


Hyperthyroidism - What it is

The thyroid is a butterfly-shaped gland situated in the front of the neck. Its main function is to produce two hormones - thyroxine and triiodothyronine - which are crucial to the control of various bodily functions. These include but are not limited to heart rate, skin, bowel activity, and muscle. 

Should the thyroid malfunction, either by underactivity or overactivity, it could cause health problems that can affect your quality of life. Thyroid hormone (TH) imbalances are usually related to autoimmune disorders - when healthy cells and tissues in your body are mistakenly attacked by your own immune system. 

Too little, too much?

When an underactive gland does not produce enough thyroid hormones to adequately meet the body's needs, the condition is referred to as hypothyroidism. Read more about hypothyroidism here.  

Conversely, in hyperthyroidism; an overactive thyroid gland results in the excessive production of thyroid hormones. Hypothyroidism and hyperthyroidism are the two most common thyroid disorders in women between the age of 20 and 50, who are also five times more likely than men to develop thyroid disorders.

Hyperthyroidism - Symptoms

The symptoms vary from person to person. Common symptoms include but are not limited to:

  • Anxiety & nervousness
  • Trembling hands
  • Weight loss
  • Hot flashes 
  • Frequent bowel movements 
  • Fast heart rate
  • Irregular menstrual periods
  • Swelling or inflammation of the eyes 
Suspect you may have hyperthyroidism? Read more under "Diagnosis".

Hyperthyroidism - How to prevent?

Hyperthyroidism - Causes and Risk Factors

There are various known causes associated with hyperthyroidism. Learn more about them below:

  • Grave's disease: Perhaps the most common cause of hyperthyroidism, Grave's disease is defined as an "autoimmune" or "self-attacking" disease where proteins (antibodies) produced by our own white blood cells overstimulate the thyroid gland to produce excess thyroid hormone which accelerates the body's metabolism. It was named after Doctor Robert Graves and accounts for at least 70% of cases 
    • Eye inflammation: Grave's disease can cause swelling and inflammation of the eyes as well as sensitivity to light and blurring or double vision
  • Toxic multinodular goiter: As we age, multiple nodules may develop in the thyroid gland which could produce excessive thyroid hormone
  • Toxic nodule: A single thyroid nodule may produce excessive thyroid hormone 
  • Excessive iodine ingestion: Drugs such as amiodarone that is high in iodine concentration could cause hyperthyroidism in certain patients

Hyperthyroidism - Diagnosis

​​Hyperthyroidism is diagnosed with blood tests that measure Thyroxine (T4) and Thyroid Stimulating Hormone (TSH). Readings that show high T4 levels and low TSH are signs of hyperthyroidism. Where required, our doctors may prescribe other tests. 

Picture showing thyroid receptor antibody (TRAb) stimulating the thyroid, causing the overproduction of thyroid hormone (T4)

Hyperthyroidism - Treatments

​There are 3 main treatments:

1. Medication

The 2 most common types of medication are beta-blockers and anti-thyroid drugs


Medication like propranolol and atenolol block the effect of the thyroid hormone on other parts of your body. While they affect the amount of thyroid hormone produced, they do not cure hyperthyroidism; thus, the condition may resurface after a patient halts the medication. 

Please note that individuals who suffer from asthma should avoid beta-blockers

Anti-thyroid Drugs

Drugs such as carbimazole, thiamazole, and propylthiouracil (PTU) act directly on the thyroid gland to effectively reduce thyroid hormone production within a few weeks. 

What are the side effects of Anti-thyroid drugs?

While uncommon, rash, itching or joint paint may occur. 

In rare cases, patients who take these medications may experience low white blood cell count or liver damage. 

2. Radioactive Iodine Therapy (RAI)

This treatment involves the use of radioactivity to destroy thyroid cells slowly over time through small doses of radioactive iodine that is absorbed by the thyroid cells. RAI is orally administered once through a small capsule. It takes about 2-3 months to achieve its full effect but will be naturally removed from the body after a few days. 

Most patients only required one dose of RAI. Occasionally, some may need more the one dose to completely treat hyperthyroidism. 

Take note that RAI is not a suitable treatment for pregnant women and young children.

What are the side effects of RAI?

As iodine is not taken up significantly by other cells, the only common side effect is underactivity of the thyroid gland (also known as hypothyroidism) where too many thyroid cells are destroyed and the remaining gland does not produce enough hormone. 

However, this condition is easily diagnosed and treated through thyroid hormone replacement. The treatment fully replaces the hormone deficiency. Thereafter, patients would only need to undergo check-ups once or twice a year. 

On the other hand, patients with Grave's disease whose eyes are significantly affected may observe that their eye health deteriorates after RAI. In these circumstances, your doctor may prescribe steroids to hinder this side effect. 

What should I do after the RAI?

Avoid close contact with pregnant women and young children for a few days by:

  • Maintaining a 1m distance 
  • Not sharing food or utensils 
Additionally, practice good general hygiene by washing your hands frequently and flushing the toilet after usage. 

Anti-thyroid Medication and RAI

One commonly asked question is: "My hormone levels are now controlled on anti-thyroid medication. Why is my doctor recommending RAI?"

In a nutshell, there is a chance that hyperthyroidism may recur once a patient ceases his medication intake. As a matter of a fact, more than 50% of all patients experience this once they stop taking anti-thyroid medication. In fact, if hypothyroidism has already recurred once, there is a 90% chance of subsequent recurrence as TSH receptor antibodies (TRAb) tend to persist in the blood stream and continuously stimulate the thyroid gland to be hyperactive. If unmanaged, this could lead to serious damage to the heart and bones. 

3. Thyroid Gland Removal Surgery 

Removal of the thyroid gland is particularly recommended for patients that:

  • Have protruding goiter where it can appear cosmetically unattractive
  • Are concerned about cancer in the thyroid 
  • Are considering pregnancy and do not want to be on anti-thyroid medication 

What are the risks of Thyroid Gland Removal Surgery? 

The potential risks include:

  • Hypothyroidism if too much thyroid tissue is removed
  • Persistent hyperthyroid if insufficient tissue is removed
  • Damage to parathyroid glands 
    • Parathyroid glands lie very close to the thyroid and control calcium levels in the blood. When damaged, they must be treated long-term with calcium and vitamin D tablets 
  •  While rare, the nerves supplying the voice box may be damaged and result in a hoarse voice

Speak to our doctors about the ideal treatment to manage hyperthyroidism. 

Hyperthyroidism - Preparing for surgery

One would need to take anti-thyroid drugs to have normalised hormone levels before undergoing surgery for thyroid gland removal. Consult our doctors about the medical prescription and instructions before the surgery. 

Hyperthyroidism - Post-surgery care

  • The surgery will leave a scar at the neck which will pale and fade after a while. While in recovery, avoid touching it
  • Avoid strenuous activities for some time 
Our doctors will provide more specific post-surgery instructions after consultation that may vary from patient to patient due to factors such as pre-existing medical conditions, etc. 

Hyperthyroidism - Other Information

Download a flyer in mandarin here:

Hyperthyroidism (Chinese).pdf

The information provided is not intended as medical advice. Terms of use. Information provided by SingHealth