Hypothyroidism (Underactive Thyroid) in Singapore

Written & reviewed by the BestDoctors.sg editorial team · Last updated 1 Sep 2026 · General information, not medical advice

An underactive thyroid is one of the most common hormone problems, and once diagnosed it is very treatable. The difficulty is that its symptoms are vague and develop slowly – which is why a blood test, not guesswork, gives the answer. This guide explains what hypothyroidism is, who is more likely to get it, what can happen if it is left untreated, how it is diagnosed and treated in Singapore, and how to live well with it.

What it is

The thyroid is a small butterfly-shaped gland in the front of the neck that sets the body’s “pace.” It makes two hormones – thyroxine (T4) and triiodothyronine (T3) – that control how quickly cells use energy, and it is itself controlled by thyroid-stimulating hormone (TSH) from the pituitary gland in the brain. In hypothyroidism the gland produces less thyroid hormone than the body needs, so metabolism and many body functions slow down. As levels fall, the pituitary releases more TSH to try to push the thyroid along – which is why a raised TSH is usually the first sign on a blood test, often before symptoms are obvious.

Symptoms

Symptoms usually develop gradually over months or years and are easy to put down to stress, ageing or a busy life. Common ones include persistent tiredness, weight gain, feeling the cold, dry skin and hair changes (including hair thinning), constipation, low mood, poor concentration or “brain fog,” a hoarse voice, puffiness of the face, muscle aches and cramps, and a slowed heart rate. In women, periods may become heavier or irregular, and an underactive thyroid can make it harder to conceive.

Not everyone has all of these, and none is unique to the thyroid – they overlap heavily with other conditions such as anaemia, depression, diabetes and the menopause, which is exactly why a blood test is needed to confirm it. Older adults may have very few symptoms, or only vague slowing-down that looks like normal ageing. Babies and young children can be affected too, which is why Singapore, like most countries, screens every newborn for congenital hypothyroidism with a heel-prick blood test.

Causes

The commonest cause worldwide and in Singapore is Hashimoto’s thyroiditis, an autoimmune condition in which the immune system gradually damages the thyroid. Other causes include:

• Thyroid surgery – removing part or all of the gland (for nodules, goitre or cancer) reduces hormone output.
• Radioactive iodine or anti-thyroid treatment for an overactive thyroid (hyperthyroidism), which can tip the gland the other way.
• Certain medicines, such as amiodarone (a heart-rhythm drug) and lithium (used in mental health).
• Thyroiditis – temporary inflammation, sometimes after a viral illness or after pregnancy (post-partum thyroiditis).
• Iodine problems – too little or, less commonly, too much iodine.
• Pituitary problems – rarely, the pituitary gland fails to signal the thyroid (“central” hypothyroidism).
• Congenital hypothyroidism – present from birth, picked up by newborn screening.

Who is at risk

Hypothyroidism can affect anyone, but it is more likely if you:

• are a woman – it is several times more common in women than men;
• are older – the risk rises with age;
• have a personal or family history of thyroid disease or other autoimmune conditions (such as type 1 diabetes, coeliac disease, vitiligo or rheumatoid arthritis);
• have recently been pregnant or given birth in the past year;
• have had thyroid surgery, radioactive iodine, or radiotherapy to the neck;
• take a medicine known to affect the thyroid;
• have Down syndrome or Turner syndrome, which carry a higher lifetime risk.

If any of these apply and you have symptoms, mention it to your doctor – it may lower the threshold for checking your thyroid.

Complications if it is not treated

Treated hypothyroidism generally causes no long-term harm. Left untreated, persistently low thyroid levels can lead to:

• Raised cholesterol and heart problems – an underactive thyroid can push up LDL (“bad”) cholesterol and is linked to heart disease.
• Goitre – the thyroid may enlarge as it works harder, causing a visible neck swelling and occasionally difficulty swallowing.
• Mental-health and memory effects – low mood, depression and slowed thinking that improve with treatment.
• Peripheral neuropathy – long-standing, poorly controlled hypothyroidism can damage nerves, causing numbness or tingling.
• Fertility and pregnancy problems – difficulty conceiving, and, in pregnancy, a higher risk of miscarriage, pre-eclampsia and effects on the baby’s development.
• Myxoedema – a rare but life-threatening extreme of untreated hypothyroidism, with intense cold intolerance, drowsiness and eventually loss of consciousness. This is a medical emergency.

How it’s diagnosed

Diagnosis is by a simple blood test measuring TSH and free T4. In primary hypothyroidism, TSH is high and free T4 is low or low-normal – a raised TSH is the earliest and most sensitive sign. Your doctor may also check thyroid antibodies (anti-TPO), which, if positive, point to Hashimoto’s as the cause and a higher chance the condition is permanent.

Because symptoms are non-specific, a doctor will often check for other causes of tiredness at the same time – such as anaemia (full blood count), blood sugar and, where relevant, vitamin levels. If the thyroid feels enlarged or a nodule is found, an ultrasound of the neck may be arranged. In Singapore, thyroid function tests are widely available through polyclinics, GPs and specialist clinics, and are usually reported within a few days.

Treatment

Hypothyroidism is treated by replacing the missing hormone with a daily tablet of levothyroxine, a synthetic form of T4 identical to what the thyroid makes. The dose is individual and is started, then adjusted, based on repeat blood tests – not on symptoms alone – until your TSH sits in the target range. Most people take it for life; the tablets simply top up what the body can no longer make.

How you take it matters. Levothyroxine works best taken on an empty stomach, at the same time each day – commonly first thing in the morning, at least 30–60 minutes before food or coffee, or at bedtime well after your last meal. Some things reduce its absorption if taken too close together, including calcium and iron supplements, some antacids, and high-fibre or soy-heavy meals – so separate these by a few hours. Tell your doctor about other medicines you take, as a few interact.

After a dose change, your doctor will usually recheck your TSH after about 6–8 weeks and fine-tune from there; once stable, testing is typically once a year. Do not stop or change the dose on your own, even if you feel well – feeling well is the goal, and it is the blood test that confirms the dose is right.

Living with hypothyroidism

Once the dose is right, most people feel back to normal and can do everything they did before. A few practical points help:

• Take it consistently. A daily routine – same time, same way – keeps levels steady. If you miss a dose, take it when you remember that day; if it is nearly the next day, skip it (do not double up) unless your doctor advises otherwise.
• Keep up your blood tests. Needs change over time – with age, weight change, other illnesses and some medicines – so periodic checks matter even when you feel fine.
• You don’t need a special diet. There is no “thyroid diet” that treats hypothyroidism. A normal, balanced diet is fine; you do not need extra iodine, and high-dose iodine or kelp/seaweed supplements can actually upset the thyroid.
• Be cautious with supplements marketed for the thyroid. “Thyroid support” products and unregulated glandular extracts are not a substitute for prescribed treatment and can be unsafe – check with your doctor first.
• Plan ahead for pregnancy. If you are trying for a baby or become pregnant, tell your doctor early, as the dose usually needs to go up and be monitored closely (see below).

Subclinical hypothyroidism and pregnancy

Subclinical hypothyroidism means a mildly raised TSH with a normal free T4 – an early or borderline picture. Depending on how high the TSH is, your symptoms, antibody status and whether you are pregnant or planning to be, your doctor may either treat it or simply monitor it with repeat tests.

Pregnancy is a special situation. The developing baby depends on the mother’s thyroid hormone, especially in early pregnancy, and requirements rise. Women already on levothyroxine usually need a dose increase as soon as pregnancy is confirmed, with more frequent blood tests, so it is important to let your doctor know promptly. Untreated or under-treated hypothyroidism in pregnancy raises the risk of complications, which is why it is watched closely.

When to see a doctor

See a doctor for a blood test if you have persistent, unexplained tiredness or a cluster of the symptoms above, particularly if you are in one of the higher-risk groups. Booking a check is also sensible if you have a neck swelling, are planning a pregnancy and have thyroid symptoms, or have a family history of thyroid disease.

Seek urgent medical care if someone with known or suspected hypothyroidism becomes very drowsy, confused, extremely cold or unresponsive – this can signal myxoedema, a rare emergency. In a medical emergency in Singapore, call 995.

Questions to ask your doctor

It helps to go in prepared. You might ask:

• What is causing my hypothyroidism, and is it likely to be permanent?
• What is my TSH target, and how often will I need blood tests?
• How and when should I take my tablet, and what should I keep it away from?
• Could any of my other medicines or supplements be affecting my thyroid?
• What should I do if I’m planning a pregnancy?
• Do I need to see an endocrinologist, or can this be managed by my GP or polyclinic?

Related conditions & guides

Learn more about the commonest cause, Hashimoto’s thyroiditis, or browse our other thyroid and hormone guides. If your main concern is a specific symptom, see our guides on brain fog and feeling the cold. Hypothyroidism is usually managed by a GP and, when needed, an endocrinologist.

Sources

This guide draws on patient information from the UK NHS (Underactive thyroid / hypothyroidism), the British Thyroid Foundation, and Singapore’s HealthHub (Health Promotion Board). It is general information and not a substitute for advice from a qualified doctor who knows your medical history.