When to suspect hyperthyroidism (weight loss, tremor) and initial tests to

When to suspect hyperthyroidism based on symptoms:

• Suspect hyperthyroidism if a person presents with one or more symptoms including weight loss (often unintentional despite increased appetite), tremor, palpitations, anxiety, heat intolerance, increased sweating, diarrhoea, fatigue, muscle weakness, and sleep disturbances.
• Additional symptoms that may raise suspicion include agitation, emotional lability, insomnia, irritability, subfertility or menstrual irregularities, polyuria, reduced libido, or gynaecomastia in men.
• In elderly patients, symptoms may be milder or nonspecific and can include deterioration of existing heart disease or new atrial fibrillation.
• Signs that support suspicion include fine tremor, warm moist skin, palmar erythema, sinus tachycardia, atrial fibrillation, and presence of goitre or thyroid nodules.
• Specific features such as thyroid eye signs (orbitopathy), including eye watering, double vision, lid retraction, lid lag, or proptosis, should prompt consideration of Graves’ disease as a cause.

These clinical features warrant assessment for hyperthyroidism especially when symptoms like weight loss and tremor are present together with cardiovascular or ophthalmic signs NICE CKS.

Initial investigations to order:

• Measure serum thyroid-stimulating hormone (TSH) as the first-line test in primary care when hyperthyroidism is suspected.
• If TSH is suppressed below the reference range, measure free thyroxine (FT4) and free triiodothyronine (FT3) levels in the same sample to confirm overt hyperthyroidism (low TSH and raised FT4/FT3) or subclinical hyperthyroidism (low TSH but normal FT4/FT3).
• Do not check thyroid function tests during acute non-thyroidal illness unless thyroid dysfunction is strongly suspected, as acute illness can transiently suppress TSH.
• If subclinical hyperthyroidism is suspected, repeat thyroid function tests after three months to confirm a persistent abnormality and exclude transient causes.
• Consider additional blood tests such as thyroid autoantibodies (TSH receptor antibodies [TRAb]) if Graves’ disease is suspected, especially in pregnancy or if thyroiditis is a differential diagnosis (inflammatory markers like ESR and CRP), or postpartum thyroiditis (thyroid peroxidase antibodies [TPOAb]).
• Perform a clinical examination including pulse, blood pressure, temperature, weight, cardiac signs, goitre or thyroid nodules assessment, and thyroid eye signs.

Further imaging such as thyroid ultrasound or radionuclide scanning is typically reserved for specialist assessment or if nodules are palpable or malignancy is suspected.

Prompt recognition of hyperthyroidism based on symptoms including weight loss and tremor, followed by TSH and reflex FT4/FT3 testing, enables timely diagnosis and management NICE CKS,NICE NG145.

Additional clinical considerations:

• Hyperthyroidism may present with liver dysfunction; baseline liver function tests should be considered as antithyroid drugs can cause hepatotoxicity, and untreated thyrotoxicosis itself can affect liver enzymes Campos et al. 2024.
• If liver dysfunction is present, careful monitoring is warranted during antithyroid treatment.
• Severe or life-threatening hyperthyroidism (thyroid storm) requires urgent specialist input and multidisciplinary management Chanhoun et al. 2026.