Hashimoto’s Thyroiditis in Singapore

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

Hashimoto’s is the underlying reason many people become hypothyroid. Understanding it explains why the condition often develops slowly, why antibodies are checked, and why some people need monitoring before any treatment.

What it is

Hashimoto’s thyroiditis (also called chronic autoimmune thyroiditis) is a long-term condition in which the immune system gradually attacks the thyroid – the small, butterfly-shaped gland in the front of the neck that makes hormones controlling how the body uses energy. Normally the immune system defends the body against infection; in Hashimoto’s it mistakenly treats healthy thyroid tissue as foreign, producing antibodies and immune cells that cause ongoing inflammation and slowly damage the gland.

Because the damage builds up quietly over a long period, the thyroid often keeps working normally at first, then produces less hormone as more tissue is affected. This is why Hashimoto’s is described as one of the most common causes of an underactive thyroid: it is the process underneath, rather than a separate illness with sudden symptoms.

How it develops

The immune attack causes chronic inflammation, which can enlarge the thyroid into a goitre (a painless swelling in the neck) and, over months to years, gradually reduce its ability to make hormone – leading to hypothyroidism. Some people pass through an early, temporary phase in which damaged tissue releases stored hormone, briefly causing overactive-thyroid symptoms, before the gland settles toward underactivity.

Progression is often slow and varies from person to person. Some people carry thyroid antibodies but keep normal thyroid levels for a long time, while others move steadily toward an underactive thyroid. This unpredictable pace is the main reason doctors repeat blood tests over time rather than assume the situation stays the same.

Symptoms

Many people have no symptoms in the early stages, or notice only a painless swelling at the front of the neck. As thyroid activity falls and hypothyroidism develops, symptoms tend to appear slowly and can be easy to put down to stress, ageing or a busy lifestyle. They mirror those of an underactive thyroid and may include:

• Persistent tiredness and low energy
• Weight gain despite no change in eating
• Feeling cold when others are comfortable
• Dry skin and brittle hair or nails
• Constipation
• Low mood, poor concentration or a sense of mental slowness
• Muscle aches, stiffness or weakness
• Heavier, irregular or more frequent periods in women

Because these symptoms overlap with many other conditions, they cannot confirm Hashimoto’s on their own – but a combination of them, especially with a neck swelling or a family history, is a good reason to arrange thyroid blood tests.

Causes and who is at risk

Hashimoto’s is an autoimmune condition, and the exact trigger is not fully understood; it is thought to result from a mix of inherited tendency and other factors that tip the immune system toward attacking the thyroid. It is not caused by anything a person did or ate, and it is not contagious.

It is much more common in women and becomes more likely with increasing age. Risk is higher with a personal or family history of thyroid or other autoimmune diseases. Having one autoimmune condition – such as type 1 diabetes, coeliac disease, vitiligo or certain other disorders – somewhat raises the chance of developing another, so doctors stay alert to overlapping symptoms in people already known to have autoimmune disease.

How it is diagnosed

Diagnosis combines thyroid function tests (which measure how active the thyroid is) with thyroid antibody tests. Raised anti-thyroid peroxidase (anti-TPO) antibodies support an autoimmune cause and help distinguish Hashimoto’s from other reasons for an underactive thyroid. In established disease the function tests show a pattern of underactivity, while positive antibodies with still-normal function point to early or as-yet-mild disease.

A neck ultrasound is sometimes used – particularly if there is a visible goitre or a lump (nodule) – to look at the size and texture of the gland and to check any nodules. In Singapore, thyroid tests can be arranged through a GP or polyclinic, with referral to an endocrinologist (a hormone specialist) when the picture is unclear, when there is a significant goitre or nodule, or when treatment needs closer supervision.

Complications and associated conditions

Treated well, most people with Hashimoto’s do very well. The concerns relate mainly to an untreated or poorly controlled underactive thyroid, which can affect the whole body over time – including the heart and how it works, and cholesterol levels, which is one reason ongoing monitoring matters. Severe complications from a very underactive thyroid are uncommon, but anyone who becomes profoundly unwell – very drowsy, confused or extremely cold – should seek urgent medical care.

Thyroid health is especially important in pregnancy. An underactive thyroid that is not properly managed can affect both mother and baby, so women with Hashimoto’s or thyroid antibodies should have their thyroid reviewed when planning a pregnancy and monitored during it. Hashimoto’s is also linked with other autoimmune conditions, so new or unexplained symptoms are sometimes worth reviewing with a doctor rather than assumed to be thyroid-related.

Treatment

When Hashimoto’s has caused the thyroid to become underactive, the treatment is thyroid hormone replacement – a daily tablet that replaces the hormone the gland can no longer make in sufficient amounts. It is usually taken long-term, often for life, because the underlying damage does not reverse. Taken consistently, it restores hormone levels to normal and typically relieves the symptoms of an underactive thyroid.

The right amount is guided by regular blood tests, and the dose may be adjusted from time to time – for example after starting treatment, during pregnancy, or if symptoms change. It is important to take the medication consistently and to change the dose only on medical advice, never by stopping or altering it independently. People who have positive antibodies but still-normal thyroid function may not need treatment yet; instead doctors monitor thyroid blood tests periodically, because there is an ongoing chance of becoming underactive over time, and treatment can begin promptly if that happens.

Living with Hashimoto’s and self-care

Living well with Hashimoto’s is mainly about steady, long-term habits rather than dramatic changes. Taking any prescribed thyroid hormone replacement consistently – ideally at the same time each day and in the way your doctor or pharmacist advises – helps keep levels stable. Keeping up with regular monitoring blood tests allows the dose to be fine-tuned and any drift toward underactivity to be caught early.

If you are planning a pregnancy or become pregnant, arrange a thyroid review early, as needs often change during this time. It is also worth mentioning any new or worsening symptoms to your doctor, since they may reflect a dose that needs adjusting or, occasionally, another linked condition. Reliable general health information for Singapore is available on HealthHub, and your GP or endocrinologist can advise on what applies to your own situation.

A note on iodine and supplements

Many products are marketed as “thyroid support” supplements, and some contain iodine or other ingredients claimed to boost thyroid function. For Hashimoto’s, these are best avoided unless a doctor advises otherwise: they do not treat the autoimmune process, and in some cases extra iodine can be unhelpful for the thyroid. A normal balanced diet usually provides what the thyroid needs. If you are considering any supplement, or already take one, discuss it with your doctor so it can be checked against your condition and any medication.

When to see a doctor

See a doctor if you notice a painless swelling in the front of your neck, have persistent symptoms of an underactive thyroid, or have a family history of thyroid or autoimmune disease together with symptoms. Speak to your doctor before conceiving or as soon as you know you are pregnant if you have known thyroid antibodies or thyroid disease, as this needs review. Severe symptoms are uncommon, but seek prompt care if you feel very unwell. Blood tests and, if needed, an ultrasound will clarify the diagnosis and guide whether treatment or monitoring is right for you.

Related conditions & guides

• Hypothyroidism (underactive thyroid)
• Thyroid disorders
• Type 1 diabetes
• Hypoglycaemia (low blood sugar)
• Diabetic neuropathy
• Diabetic foot problems
• Addison’s disease
• Pituitary tumours
• Acromegaly
• Prolactinoma & high prolactin
• Preventing type 2 diabetes
• Endocrinologists in Singapore

Sources

• American Thyroid Association — Hashimoto’s thyroiditis (autoimmune definition; commonest cause of hypothyroidism; goitre; TSH/free T4/antibody/ultrasound diagnosis; levothyroxine).
• NHS — underactive thyroid (Hashimoto’s as primary cause; predominance in women; family/autoimmune risk).
• SingHealth (HealthXchange / SGH Endocrinology), Singapore — Hashimoto’s as the most common cause of hypothyroidism.