Hyperthyroidism/ Overactive Thyroid

What is Hyperthyroidism?

What causes Hyperthyroidism?

In Singapore, hyperthyroidism is a relatively common endocrine disorder, with Graves’ disease being the most frequent cause. However, some of the other common causes include:

• Graves’ disease – this autoimmune disorder is the most frequent cause of hyperthyroidism. The immune system mistakenly attacks the thyroid gland, stimulating it to produce too much hormone.

• Excessive iodine intake – iodine is essential for thyroid hormone production, but excessive intake through medication such as amiodarone or very rarely diet can trigger hyperthyroidism.

• Thyroiditis – inflammation of the thyroid, often caused after a viral infection and is autoimmune in nature. It results in the excessive release of stored thyroid hormone.

• Toxic thyroid nodules – Benign lumps can be functional and produce excess thyroid hormones. Dr Dinesh commented that most thyroid nodules are non-functional.

• Overmedication with thyroid hormones – taking too much levothyroxine, that is used to treat hypothyroidism, can lead to an overactive thyroid.

What are the symptoms of Hyperthyroidism?

The symptoms of hyperthyroidism can vary from person to person. Additionally, these symptoms can either develop gradually or suddenly, which can be:

• Anxiety, irritability or nervousness.
• Difficulty sleeping (insomnia).
• Fatigue or muscle weakness.
• Goitre (enlarged thyroid gland).
• Heat intolerance and excessive sweating.
• Increased bowel movements/ loose bowel action.
• Menstrual irregularities and sometimes cessation of periods.
• Rapid or irregular heartbeat (palpitations).
• Tremors, particularly in the hands.
• Thinning hair and brittle nails.
• Unexplained weight loss, despite normal or increased appetite.

Endocrinologist, Dr Dinesh Mahendran finds the most common symptoms are a feeling that life is more stressful, loss of weight and increased bowel movements. When it gets more severe, palpitations are the predominant symptom. 

Who is at risk of Hyperthyroidism in Singapore?

Although hyperthyroidism can develop in anyone, there are certain individuals who are more predisposed due to genetic, hormonal or environmental factors. As such, recognising these risk groups is key to promoting early detection, and preventing long-term complications, especially in a fast-paced urban setting like Singapore, where symptoms may be mistaken for stress or lifestyle-related issues. Dr Dinesh commented that patients don’t mind the weight loss, and he has to counsel his patients on why it is an unhealthy weight loss and that treatment is crucial to prevent long-term irreversible changes to the body. 

Some individuals who are more likely to develop hyperthyroidism include:

• Gender – hyperthyroidism is significantly more common in women. This is due to hormonal differences, genetic variations and the unique characteristics of the female immune system. Women are therefore more prone to all autoimmune conditions including Graves’ disease, which is the most common cause of hyperthyroidism.

• Family history – a genetic predisposition can increase the risk. If close family members have hyperthyroidism, Graves’ disease or other thyroid disorders, there is a higher likelihood of developing a similar condition due to inherited immune/ genetic traits. Dr Dinesh mentioned that he often finds his patients’ having an affected auntie or sister and it could even be the opposite condition (an underactive thyroid- hypothyroidism).

• Medications – drugs such as amiodarone, that is used for heart rhythm problems, may affect thyroid function, and potentially lead to overactivity of the gland.

• Autoimmune diseases – individuals with autoimmune conditions such as type 1 diabetes, pernicious anaemia, rheumatoid arthritis or vitiligo are at increased risk of developing Graves’ disease. This is because autoimmune disorders often occur together, as part of a broader immune system imbalance.

• Thyroid nodules or multinodular goitre – nodules or abnormal growths in the thyroid can be overactive, producing overproducing thyroid hormones independent of normal regulation. This can lead to solitary toxic nodules (one culprit nodule only) or toxic multinodular goitre (multiple culprits), a non-autoimmune form of hyperthyroidism more commonly seen in older adults.

• Postpartum women – some women experience thyroid dysfunction within the first year after giving birth. This condition, known as postpartum thyroiditis, may initially cause a temporary phase of hyperthyroidism before the thyroid normalises or shifts into hypothyroidism. Dr. Dinesh finds that the most common symptom is excessive weight loss after giving birth.

• High iodine intake – although iodine is essential for thyroid hormone production, rarely excessive amounts, often from supplements or contrast dyes used in imaging, can trigger hyperthyroidism in susceptible individuals, often in those with pre-existing predisposition to hyperthyroidism (for example functional nodules).

What are the complications associated with Hyperthyroidism?

Delaying treatment for hyperthyroidism can lead to a range of serious health complications. These complications arise because excess thyroid hormones overstimulate various body systems, especially the heart, bones, muscles and nervous system.

Some of the potential complications include:

• Eye problems (in Graves’ disease) – Graves’ orbitopathy can cause irreversible bulging eyes, dryness, redness, double vision, and in severe cases, vision loss. These symptoms occur due to inflammation, and swelling in the eye muscles, and surrounding tissues.

• Emotional and cognitive disturbances – hyperthyroidism can affect brain function, and mental wellbeing. Many patients experience mood swings, anxiety, restlessness, irritability, and difficulty concentrating. For some individuals, symptoms may mimic or worsen existing mental health conditions.

• Heart issues – one of the most significant risks. High levels of thyroid hormones increase heart rate, and the force of heart contractions. Over time, this can lead to persistent tachycardia, atrial fibrillation (an abnormal rhythm that is one of the most common causes of stroke), and eventually heart failure, particularly in older adults or those with underlying cardiac conditions. This can be lethal. Even mild hyperthyroidism (subclinical hyperthyroidism) can cause atrial fibrillation and subsequent stroke.

• Menstrual and fertility issues – excess thyroid hormones can disrupt reproductive hormones, leading to irregular or absent periods, reduced ovulation, and fertility challenges in both women and men.

• Muscle weakness and fatigue – ongoing hormonal excess may cause progressive muscle breakdown, particularly in the upper arms, and thighs. This can result in weakness, difficulty climbing stairs, and reduced mobility.

• Osteoporosis – thyroid hormones accelerate bone loss, exceeding the body’s mechanisms of repair and bone growth. This increases the risk of low bone density, and fractures, especially in postmenopausal women, and the elderly.

• Pregnancy complications – poorly controlled hyperthyroidism increases the risk of miscarriage, premature labour, pre-eclampsia, low birth weight, and abnormal foetal thyroid development.

• Thyroid storm – a rare but life-threatening medical emergency. Thyroid storm is an extreme form of hyperthyroidism, marked by dangerously high levels of thyroid hormones. It can cause fever, agitation, confusion, rapid heart rate, and even organ failure, prompting immediate hospital treatment in intensive care.

How is Hyperthyroidism diagnosed?

Hyperthyroidism is diagnosed through a combination of clinical assessment, blood tests, and imaging tests. Since many of its symptoms overlap with other medical conditions, a thorough evaluation is essential to confirm the diagnosis, and identify the underlying causes.

TEST	PURPOSE	HOW IT HELPS
Thyroid Function Test (TFT)	To assess thyroid hormone levels.	This blood test measures levels of thyroid hormones (free T3, and free T4), along with thyroid-stimulating hormone (TSH). In hyperthyroidism, TSH is typically suppressed, while T3 and/or T4 are elevated.
Thyroid Antibody Test	To detect autoimmune causes.	If Graves’ disease is suspected, blood tests may be used to detect thyroid receptor antibodies (TRAB) which is diagnostic.
Radioactive Iodine Uptake (RAIU) Scan	To identify the cause of hyperthyroidism.	This scan evaluates how much iodine the thyroid absorbs. High uptake may indicate Graves’ disease, while low uptake suggests thyroiditis or excess hormone intake. This is the first-line test in hyperthyroidism diagnosis.
Electrocardiogram (ECG)	To monitor heart rhythm.	Hyperthyroidism can affect the heart. An ECG may be performed to detect arrhythmias such as atrial fibrillation.
Thyroid Ultrasound	To examine the thyroid gland’s structure.	An ultrasound helps visualise the thyroid, and can detect nodules, enlargement or inflammation. It is useful prior to surgery or radioactive iodine if required to ensure no other thyroid issue co-exists.

How is Hyperthyroidism treated?

Treatment for hyperthyroidism focuses on restoring normal thyroid hormone levels, managing symptoms, and addressing the root cause of the condition. Treatment approaches may include one of a combination of the following options:

Medication

• Anti-thyroid drugs – medications such as carbimazole reduce the production of thyroid hormones. These are often the first line of treatment, and may be continued for 12 to 18 months. If our doctors proceed with prescribing anti-thyroid drugs, regular monitoring is required to adjust the dose as every patient requires a different dose and doses are reduced as the condition gets better aiming for eventual cessation where possible.

• Beta-blockers – these do not reduce thyroid hormone levels but help relieve symptoms such as rapid heartbeat, anxiety, and tremors. They are often used short-term while waiting for anti-thyroid medications to take effect and cause the greatest improvement to symptoms initially 

• Radioactive Iodine Therapy – radioiodine is taken orally, and destroys overactive thyroid cells. It is a highly effective, and commonly used treatment in adults with Graves’ disease or toxic nodules. Most patients respond well within 6 to 12 weeks. The aim is to achieve hypothyroidism and the patient will require life-long thyroxine hormone replacement. Dr. Dinesh commented that although one medication (carbimazole) is swapped for another, thyroid levels then become indefinitely normal and the long-term side effects of hyperthyroidism are mitigated. 

Surgery (Thyroidectomy)

Surgical removal of part or all the thyroid gland is considered in certain cases of hyperthyroidism. This treatment option is typically recommended when other approaches, such as medications or radioactive iodine therapy, are unsuitable or ineffective. Surgery may also be necessary in specific situations, such as:

• Failed Response to Other Treatments – for patients who do not respond to or cannot tolerate anti-thyroid medications or radioactive iodine therapy, surgery offers a definitive solution.

• Large Goitre – if the thyroid gland has become enlarged, and is causing compression on surrounding structures such as the trachea (windpipe) or oesophagus (food pipe), surgery may be required to relieve symptoms like difficulty swallowing or breathing.

• Pregnancy – if a pregnant woman has severe hyperthyroidism that cannot be controlled with medication, surgery may be recommended as the safest treatment option for both the mother, and baby.

• Suspicion of Thyroid Cancer – if there is concern that a thyroid nodule may be cancerous, surgical removal of the affected part or the entire thyroid gland is often performed to remove the tumour, and prevent the spread of cancer.

How is thyroidectomy performed?

Thyroidectomy is typically performed under general anaesthesia by a specialised thyroid surgeon. There are two main types of thyroid surgery:

• Partial Thyroidectomy – removal of a portion of the thyroid gland, usually in cases of benign conditions or when only one lobe is affected. This is done in patients with solitary toxic adenoma (one functional nodule on one lobe) and not done for autoimmune hyperthyroidism as the hyperthyroidism often recurs.

• Total Thyroidectomy – removal of the entire thyroid gland, often indicated when the condition is more severe, such as in cases of thyroid cancer or diffuse, unmanageable hyperthyroidism.

The procedure is usually done through a small incision made across the front of the neck. In less severe or complex cases, minimally invasive techniques, such as robotic or laparoscopic surgery, may be used, which require smaller incisions, and generally result in quicker recovery times. After surgery, patients are monitored in the hospital for a short period, and follow-up care includes checking thyroid hormone levels to adjust medication as necessary. If this is required, Dr Dinesh will refer you to a sub-specialised surgeon.

Lifestyle and Nutritional Support

• Avoid excessive iodine intake – certain supplements or diets high in iodine can worsen hyperthyroidism.
• Maintain balanced nutrition – to support general wellbeing, and manage symptoms like weight loss or muscle weakness.
• Stress management – chronic stress can aggravate symptoms or make hyperthyroidism harder to deal with. To help control your stress levels, do practice mindfulness, exercise regularly, and ensure you get adequate sleep.

Monitoring and Follow-up

• Regular thyroid function tests – to monitor hormone levels, and ensure that treatment remains effective and well-tolerated.
• Heart health monitoring – especially in older adults or those with arrhythmias.
• Bone health assessment – in long-standing hyperthyroidism or in older individuals, bone density may be monitored to detect early signs of osteoporosis.

Summary

Hyperthyroidism is treatable, but the key to effective management is early detection. If you are experiencing symptoms like unexplained weight loss, rapid heartbeat, heat intolerance or irritability, do not wait for them to worsen. These could be signs of overactive thyroid, and acting now can prevent more serious health issues down the road.

At The Metabolic Clinic, our clinical team is dedicated to providing personalised treatment plans, and ongoing support to help you regain control of your thyroid health. Schedule an appointment with us today to start your journey toward a healthier, more balanced you.

Frequently Asked Questions