General Health

Thyroid Disease: Symptoms, Tests, and Treatment

A patient-friendly guide to thyroid disease, including hypothyroidism, hyperthyroidism, thyroid nodules, blood tests, symptoms, treatment options, pregnancy considerations, and when to seek help.

16 min read

Introduction

The thyroid is a small, butterfly-shaped gland at the front of the neck. It produces hormones that influence almost every system in the body — metabolism, energy, heart rate, temperature regulation, mood, digestion, and more. When the thyroid produces too little or too much hormone, or when structural changes affect it, the impact can be wide-ranging.

Thyroid disease is common. Hypothyroidism (underactive thyroid) affects roughly 1 in 20 adults in many countries and is considerably more common in women and in older age groups. Hyperthyroidism (overactive thyroid), thyroid nodules, and autoimmune thyroid conditions are also among the more frequently encountered conditions in primary care.

This guide explains the main types of thyroid disease — what they are, what symptoms they cause, how they are diagnosed, how they are treated, and when to seek urgent attention.

Key Points

  • The thyroid gland produces hormones that regulate metabolism, heart rate, energy, temperature, and many other body functions
  • Hypothyroidism (underactive thyroid) and hyperthyroidism (overactive thyroid) are the most common thyroid disorders
  • Thyroid symptoms — including fatigue, weight change, palpitations, and mood changes — are non-specific and overlap with many other conditions; testing is needed to confirm a thyroid cause
  • Blood tests (TSH and free T4) are the standard starting point for assessing thyroid function
  • Autoimmune conditions, including Hashimoto’s thyroiditis and Graves’ disease, are the most common causes of thyroid dysfunction in high-income countries
  • Thyroid disease is more common in women, during and after pregnancy, and with advancing age
  • Most thyroid conditions are manageable with treatment; do not stop or change thyroid medication without clinical guidance
  • Thyroid nodules are common, usually benign, and most require monitoring rather than immediate intervention

What the Thyroid Does

The thyroid gland sits at the front of the neck, below the larynx (voice box). It produces two primary hormones: thyroxine (T4) and triiodothyronine (T3). These hormones are released into the bloodstream and affect virtually every cell in the body.

Thyroid hormone regulates:

  • Metabolism — the rate at which cells use energy
  • Heart rate and heart rhythm
  • Body temperature
  • Digestion and bowel function
  • Muscle function and strength
  • Mood and cognitive function
  • Menstrual cycle regularity
  • Cholesterol levels
  • Growth and development (particularly important in foetal development and childhood)

The thyroid is regulated by the pituitary gland, which produces thyroid-stimulating hormone (TSH). When thyroid hormone levels fall, TSH rises to prompt the thyroid to produce more. When thyroid hormone levels are high, TSH falls. This feedback relationship is the basis for the TSH blood test used to screen thyroid function.

Main Types of Thyroid Disease

Hypothyroidism

The thyroid produces too little hormone. Metabolism slows, affecting energy, temperature regulation, heart rate, mood, and many other functions.

Hyperthyroidism

The thyroid produces too much hormone. The body’s systems are driven faster than normal — raising heart rate, accelerating metabolism, and affecting mood, weight, and sleep.

Thyroiditis

Inflammation of the thyroid gland. This can be autoimmune, postpartum, or caused by a viral infection. Some forms cause a temporary hyperthyroid phase followed by a hypothyroid phase.

Thyroid Nodules and Goitre

A goitre is an enlarged thyroid gland. Thyroid nodules are discrete lumps within the thyroid. Both are common and usually benign, but require assessment.

Thyroid Cancer

Thyroid cancer is among the less common thyroid conditions. It often presents as a thyroid nodule and is usually detected during assessment of a neck lump. It is not covered in depth in this guide — if thyroid cancer has been raised as a possibility, your care team will provide specific information and specialist referral.

Hypothyroidism

Hypothyroidism occurs when the thyroid does not produce enough hormone. The most common cause in high-income countries is Hashimoto’s thyroiditis, an autoimmune condition in which the immune system attacks the thyroid gland over time, gradually reducing its ability to produce hormone.

Symptoms

Because thyroid hormone affects many body systems, the symptoms of hypothyroidism can be broad and easily attributed to other causes:

  • Fatigue and low energy — often the most prominent symptom; characteristically does not improve with rest
  • Weight gain or difficulty losing weight — due to slowed metabolism
  • Cold intolerance — feeling cold when others are comfortable
  • Constipation
  • Dry skin and brittle nails
  • Hair thinning or hair loss
  • Heavy or irregular menstrual periods
  • Low mood or depression-like symptoms
  • Cognitive slowing — sometimes described as “brain fog”
  • Slow heart rate (bradycardia)
  • Raised cholesterol — underactive thyroid can elevate LDL cholesterol
  • Muscle aches or stiffness
  • Puffiness around the face and eyes

These symptoms are common and overlap with many other conditions. Fatigue, low mood, and weight change in particular have numerous other potential causes. Testing is needed to confirm whether the thyroid is contributing.

See Why Am I Always Tired? if fatigue is a primary concern, and Depression: Symptoms, Causes, and Treatment if low mood is prominent.

Hyperthyroidism

Hyperthyroidism occurs when the thyroid produces too much hormone. The most common cause is Graves’ disease, an autoimmune condition in which antibodies stimulate the thyroid to overproduce hormone. Other causes include toxic nodular goitre and thyroiditis.

Symptoms

An overactive thyroid drives the body’s systems faster than usual:

  • Anxiety and restlessness — sometimes difficult to distinguish from an anxiety disorder without testing
  • Palpitations — awareness of a rapid, forceful, or irregular heartbeat
  • Tremor — particularly of the hands
  • Sweating and heat intolerance
  • Unintentional weight loss despite normal or increased appetite
  • Diarrhoea or frequent bowel movements
  • Sleep difficulties
  • Lighter or irregular menstrual periods
  • Fatigue — despite feeling driven, the body is using energy inefficiently
  • Irritability and emotional lability
  • Muscle weakness

Hyperthyroidism is a recognised risk factor for atrial fibrillation — an irregular heart rhythm that requires separate assessment and management. See Atrial Fibrillation: Symptoms, Risks, and Treatment and Heart Palpitations: When to Worry.

Symptoms such as anxiety, palpitations, and weight loss have many causes. Testing is needed to determine whether the thyroid is responsible. See Anxiety Disorders if anxiety is a primary concern.

Thyroiditis

Thyroiditis refers to inflammation of the thyroid gland. There are several forms:

Autoimmune Thyroiditis (Hashimoto’s)

The most common form. The immune system produces antibodies against the thyroid, gradually impairing its ability to produce hormone. Most people with Hashimoto’s develop hypothyroidism over time. The condition is often identified on blood tests done for other symptoms.

Postpartum Thyroiditis

Postpartum thyroiditis affects around 5–10% of women in the year after giving birth. It occurs when the immune system — which is partially suppressed during pregnancy — rebounds after delivery, and in some women this triggers thyroid inflammation.

The condition often progresses through phases:

  1. A hyperthyroid phase (weeks to months after delivery) — fatigue, irritability, palpitations, or anxiety
  2. A hypothyroid phase (typically 4–8 months postpartum) — fatigue, low mood, weight gain
  3. Recovery in most cases, though some women remain hypothyroid

The symptoms of postpartum thyroiditis can be mistaken for postpartum depression or anxiety. If mood, energy, or anxiety symptoms persist after birth, thyroid testing is a reasonable part of the clinical assessment. See Postpartum Depression: Symptoms, Risks, and Treatment.

Subacute (De Quervain’s) Thyroiditis

Usually triggered by a viral infection. Causes a painful or tender thyroid, often with a period of hyperthyroid symptoms followed by hypothyroidism, before most people recover full thyroid function. Managed with anti-inflammatory medicines and, if needed, treatment of thyroid dysfunction during the active phases.

Thyroid Nodules and Goitre

Thyroid Nodules

Thyroid nodules — discrete lumps within the thyroid gland — are common. Studies using imaging find nodules in a large proportion of adults, particularly women and older individuals. The vast majority are benign.

However, nodules warrant assessment because a small proportion are cancerous. Assessment is generally indicated when a nodule is:

  • Newly discovered or growing in size
  • Firm or hard on examination
  • Associated with voice changes, difficulty swallowing, or neck discomfort
  • Detected in someone with risk factors for thyroid cancer (such as a history of neck radiation or certain family cancer syndromes)

Assessment typically involves thyroid ultrasound and sometimes fine-needle aspiration biopsy to sample cells. Most benign nodules are monitored with periodic imaging rather than requiring surgery.

Goitre

A goitre is an enlargement of the thyroid gland. It can occur with underactive, overactive, or normal thyroid function. Causes include iodine deficiency (in regions where this is common), autoimmune thyroid disease, and nodular changes.

A large goitre may cause a visible neck swelling, a sensation of pressure in the throat, difficulty swallowing, or voice changes. Goitres that cause symptoms, grow rapidly, or feel firm require prompt assessment.

Causes and Risk Factors

Autoimmune Conditions

Autoimmune thyroid disease is the most common cause of both hypothyroidism (Hashimoto’s) and hyperthyroidism (Graves’ disease) in high-income countries.

Family History

A family history of thyroid disease, particularly autoimmune thyroid conditions, increases the likelihood of developing thyroid problems.

Pregnancy and the Postpartum Period

Pregnancy and the postpartum period are associated with significant changes in thyroid function. Postpartum thyroiditis is estimated to affect up to 1 in 10 women. People with a personal or family history of autoimmune thyroid disease are at higher risk.

Iodine

Iodine is an essential dietary element for thyroid hormone production. Both iodine deficiency (causing goitre and hypothyroidism) and iodine excess can affect thyroid function. Iodine deficiency is uncommon in countries with iodised salt but remains relevant in some populations.

Certain Medicines

Some medicines can affect thyroid function or test results — including amiodarone (a heart medicine), lithium, and certain imaging contrast agents. If you are on any of these medicines and have thyroid symptoms, discuss this with your prescribing clinician. See Medication Safety: How to Avoid Common Medicine Problems for general information about medicine interactions and safety.

Previous Thyroid Surgery or Radiation

Thyroid surgery (including partial or total thyroidectomy) and radiation to the head or neck area can result in hypothyroidism requiring long-term hormone replacement.

Age and Sex

Thyroid disease is significantly more common in women than men, and incidence increases with age. Autoimmune thyroid conditions in particular are predominantly diagnosed in women.

Diagnosis

TSH (Thyroid-Stimulating Hormone)

TSH is the single most useful initial test for assessing thyroid function. A raised TSH generally indicates an underactive thyroid; a suppressed TSH generally indicates an overactive thyroid. TSH is a sensitive marker and is usually the first test ordered when thyroid disease is suspected.

Free T4

Free T4 (free thyroxine) measures the active thyroid hormone circulating in the blood. It helps confirm and characterise thyroid dysfunction identified on TSH testing.

Free T3

Free T3 is sometimes measured in specific situations — for example, when hyperthyroidism is suspected but free T4 is normal, or in monitoring of certain thyroid conditions.

Thyroid Antibodies

Antibodies such as anti-thyroid peroxidase (anti-TPO) antibodies indicate autoimmune thyroid disease. They are useful for confirming the cause of hypothyroidism (Hashimoto’s) and for risk-stratifying subclinical thyroid dysfunction.

Thyroid Ultrasound

Ultrasound is the imaging method of choice for assessing thyroid nodules and goitre. It shows the size and characteristics of the thyroid and any nodules within it. It does not measure thyroid hormone levels.

Radioactive Iodine Uptake Scan

Used in selected cases of hyperthyroidism to determine whether the whole gland is overactive or whether a specific nodule is producing excess hormone. This helps guide treatment choices. It is not a routine thyroid screening test.

Treatment

Hypothyroidism

Hypothyroidism is treated with thyroid hormone replacement — a synthetic form of thyroxine taken orally. Most people require ongoing treatment. Blood tests are used to monitor thyroid levels and adjust the dose over time.

Some people experience residual symptoms despite blood test results in the normal range; this is an area for clinical discussion with your care team.

Do not stop or change thyroid hormone medication without advice from your clinician. Dose changes need monitoring to ensure thyroid levels remain within a safe range.

Hyperthyroidism

Treatment options include:

  • Antithyroid medicines — these reduce thyroid hormone production. They are usually the first-line treatment, particularly in younger patients and during pregnancy. Regular blood test monitoring is required.
  • Radioactive iodine — taken orally, it is absorbed by the thyroid and gradually reduces its activity. This often results in hypothyroidism over time, requiring long-term replacement treatment.
  • Surgery (thyroidectomy) — removal of part or all of the thyroid gland. Used in specific situations such as large goitres, nodular hyperthyroidism, or when other treatments are not appropriate.
  • Beta-blockers — used for symptom relief (reducing heart rate, tremor, and palpitations) while awaiting the primary treatment to take effect. They do not treat the underlying thyroid disorder.

Thyroiditis

Treatment depends on the cause and phase. Subacute thyroiditis causing pain may be managed with anti-inflammatory medicines. During hyperthyroid or hypothyroid phases, thyroid levels are monitored; treatment may or may not be needed depending on severity. Many cases of postpartum and subacute thyroiditis resolve, though some individuals develop permanent hypothyroidism.

Thyroid Nodules

Management depends on the characteristics of the nodule:

  • Monitoring — benign-appearing nodules are usually watched with periodic ultrasound
  • Fine-needle aspiration biopsy — for nodules with features that require further assessment
  • Surgery — if biopsy shows cancer, results are inconclusive for certain types, or if a nodule causes significant symptoms

Pregnancy and Postpartum Considerations

During Pregnancy

Thyroid hormone requirements increase during pregnancy. The thyroid must produce more hormone to support both the pregnant person and the developing baby, particularly in the first trimester before the baby develops its own thyroid function.

  • People with pre-existing hypothyroidism typically need a dose increase during pregnancy
  • Untreated or undertreated hypothyroidism in pregnancy is associated with risks to the developing baby’s neurological development
  • Hyperthyroidism in pregnancy requires careful management with medicines appropriate in pregnancy
  • Thyroid function tests use different reference ranges in pregnancy; results should be interpreted with this in mind

If you have known thyroid disease and are planning pregnancy or become pregnant, inform your care team early so thyroid levels can be assessed and treatment adjusted if needed.

Postpartum

Postpartum thyroiditis is common and frequently unrecognised (see the Thyroiditis section above). Its symptoms — fatigue, mood changes, anxiety, and cognitive difficulty — overlap substantially with those of postpartum depression and the normal demands of new parenthood.

If mood, energy, or anxiety symptoms are persistent or significant after birth, thyroid function testing is a reasonable and simple part of the clinical assessment alongside standard depression screening.

For pregnancy-related metabolic health and diabetes, see Gestational Diabetes: Screening, Treatment, and Follow-Up. For postnatal mood, see Postpartum Depression: Symptoms, Risks, and Treatment.

Thyroid Symptoms Are Not Always Thyroid Disease

Fatigue, anxiety, weight change, palpitations, low mood, and menstrual irregularity are among the most common symptoms people experience — and they have many possible causes beyond the thyroid.

The same symptoms appear across:

  • Depression and anxiety disorders
  • Iron deficiency anaemia
  • Sleep disorders (particularly obstructive sleep apnoea)
  • Perimenopause and menopause
  • Diabetes and prediabetes
  • Other medical conditions

This means:

  • Thyroid tests can come back normal even when symptoms are significant and real — the thyroid is one possible cause among many
  • A normal thyroid result should prompt investigation of other causes, not reassurance that nothing is wrong
  • An abnormal thyroid result does not mean the thyroid is the only cause, particularly when several conditions may coexist

Testing and clinical assessment — not symptoms alone — are needed to determine whether the thyroid is contributing. If you have persistent unexplained symptoms, a comprehensive assessment is appropriate.

See Why Am I Always Tired? for a broader guide to investigating persistent fatigue, and Women’s Health Hub for hormonal and reproductive causes of overlapping symptoms.

When to Seek Urgent Help

Most thyroid disease is managed in the outpatient setting. However, seek urgent medical attention if you experience:

  • Severe palpitations, chest pain, or a very fast or irregular heartbeat
  • Fainting or collapse
  • Severe breathlessness at rest
  • Confusion, extreme agitation, or high fever in someone known to have hyperthyroidism — these may indicate thyroid storm (thyrotoxic crisis), a rare but life-threatening emergency
  • Severe weakness, drowsiness, or abnormally low body temperature in someone known to have hypothyroidism — rarely, profound hypothyroidism can progress to a medical emergency
  • Rapidly enlarging lump in the neck
  • Difficulty swallowing or breathing due to neck swelling
  • Voice change developing alongside a thyroid swelling

If you are uncertain whether your symptoms need urgent attention, seek medical review promptly rather than waiting.

Further Reading

Educational only; not a substitute for professional medical advice. Thyroid disease management should be guided by your clinical care team.