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Hyperthyroidism (Thyrotoxicosis)

 

This guideline applies to adults aged 18 and over.

 

Introduction

Thyrotoxicosis is defined by suppressed TSH with raised free T4 and/or T3. It commonly presents with symptoms such as weight loss, anxiety, heat intolerance, tremor, and palpitations. Prompt assessment and appropriate referral are essential.

 

In scope

  • Overt Hyperthyroidism (suppressed TSH with elevated free T4 and/or T3)
     
  • Subclinical Hyperthyroidism (low TSH with normal fT4, fT3)

 

Not in scope

  • Children with thyroid disease


 

Red Flag Features

This list is non-exhaustive

  • Symptoms suggestive of thyroid cancer e.g. neck lumps/ goiters, dysphagia/ hoarseness/ stridor
     
  • Symptoms suggestive of thyroid storm e.g. sudden and severe agitation/ delirium, tachycardia, atrial fibrillation, hyperthermia, nausea and vomiting, tremor
     
  • Symptoms suggestive of agranulocytosis (fever, sore throat, flu like symptoms, skin infection or mouth ulcers), pancreatitis of hepatic impairment if patient on carbimazole

 

Investigations Required Prior to Referral

  • TSH, Free T4, Free T3
    (Note: Free T3 only analysed if Free T4 is normal/near normal)
     
  • TSH receptor antibodies
     
  • Pregnancy test if appropriate
     
  • FBC, U&E, LFT
     
  • Do NOT request:
    • Thyroid ultrasound
    • Radionuclide uptake scan

 

Management Optimization

While awaiting review with endocrine adopt a shared decision-making approach
Refer to national guidance as well as the below guidance

 

Symptom Relief

  • Consider propranolol for symptomatic relief of tremor or tachycardia in all patients if no contraindications. See BNFfor dosing.

 

Initiating Carbimazole in Primary Care – Two Options

Option 1: GP confident in initiating carbimazole

If the GP has experience and feels confident in initiating treatment, carbimazole can be started at the same time as referring to endocrine if ALL of the following criteria are met:

 

1.Diagnosis confirmed

a) Suppressed TSH with elevated Free T4 and/or Free T3

 

2.Symptomatic

a) Moderate to severe symptoms (e.g. palpitations, tremor, weight loss, significant anxiety)

 

3.Biochemically significant

a) Free T4 >30 pmol/L OR Free T3 >10 pmol/L

 

4.Baseline investigations completed

a) TSH receptor antibodies have been requested
 

b) FBC and LFTs, U&Es done and acceptable

 

5.Not pregnant

a) If pregnant or planning pregnancy: urgent referral, do not initiate

 

6.Informed consent

a) Patient counselled regarding side effects, including agranulocytosis risk and signs (high fevers, sore throat, mouth ulcers, flu like symptoms or skin infections)

 

7.Referral to endocrine

a) Patient is being referred to endocrine for ongoing management

 

 

Initiation Advice:

  • Start carbimazole 20 mg once daily if above criteria are met Carbimazole | Drugs | BNF | NICE

  • Book repeat TFTs in 4–6 weeks
     
  • If T4 >30 or T3 >10 at 4–6 week review → increase carbimazole to 30 mg daily
     
  • If TSH >10 → stop carbimazole and repeat TFTs
     
  • Monitor TFTs every 4-6 weeks until endocrine review and adjust dose accordingly. If unsure then do not make changes and seek advice via endocrine advice and guidance.

 

Monitoring and safety advice:

  • If signs of symptoms or agranulocytosis, pancreatitis or hepatic impairment then stop carbimazole and follow Kernow formulary guidance: Guidance for monitoring drug therapy in adults.
     
  • If patient is acutely unwell with agranulocytosis, pancreatitis or hepatic impairment arrange same day acute medical admission (see emergency referrals below)
     

Important patient Information:

  • Reinforce the need for regular blood monitoring
     
  • To inform healthcare providers they are on carbimazole, especially if acutely unwell or admitted
     
  • Patients should be clearly informed of the rare but serious risks of:
    • Agranulocytosis:
      • Instruct them to seek urgent medical attention and an FBC if they develop a fever, sore throat, flu like symptoms, skin infection or mouth ulcers.
    • Pancreatitis:
      • Instruct them to seek urgent medical attention if they develop abdominal pain, vomiting, fevers or jaundice
    • Hepatic impairment
      • Instruct them to seek urgent medical attention if they develop symptoms such as jaundice, unexplained dark urine or pale stools, itching or right upper quadrant pain



Option 2: GP with limited experience using carbimazole or diagnostic uncertainty

If the GP is not confident in initiating treatment or it does not meet the above criteria (e.g. borderline TSH/T4 or asymptomatic) then seek advice from Endocrinology Advice & Guidance (A&G) prior to initiating treatment.

 

Atrial fibrillation:

 

Subclinical hyperthyroidism

Subclinical Hyperthyroidism is defined as low TSH with normal fT4, fT3

  • Assess for clinical features of hyperthyroidism & thyroid cancer
     
  • Assess for other causes of low TSH
    • Non thyroid illness
    • Drugs-supressing TSH: glucocorticoids, dopaminergic [anti-parkinsonian] medication, or octreotide)
    • Drugs that alter thyroid hormone secretion (lithium, amiodarone, and iodide in contrast media dyes)
  • If other causes excluded, initially rpt TFTS in 3-6months ( sooner if elderly or cardiovascular disease) and refer if persistent


 

Advice and Guidance

Use the Endocrine A&G service if:

  • Clinical or biochemical deterioration occurs while awaiting referral
     
  • There is uncertainty about diagnosis or treatment suitability
     
  • Advice is required before starting or changing treatment in primary care


 

Referral

Emergency and Red Flags

  • Thyroid storm – admit immediately via Acute GP/ ED / 999 depending clinical assessment
     
  • Agranulocytosis, pancreatitis or hepatic impairment on carbimazole (see above) and acutely unwell – admit immediately via Acute GP/ ED / 999 depending clinical assessment
     
  • Suspected thyroid malignancy – refer via Fast Track Suspected Cancer Head and Neck pathway

 

Urgent Referral Criteria

  • Pregnancy with hyperthyroidism – urgent joint referral to Endocrinology and Antenatal Clinic
     
  • Amiodarone-induced hyperthyroidism
     
  • Neutropenic with hyperthyroidism (in a systemically well patient)

 

Routine Referral Criteria

  • Overt hyperthyroidism (TSH suppressed, Free T4 and/or T3 elevated)
     
  • Persistent subclinical hyperthyroidism after 3–6 months) (See below)
    • Refer sooner if elderly or with cardiovascular risk factors

 

Information Required with Referral

  • Most recent TFTs
     
  • TSH receptor antibody result
     
  • FBC, U&Es, LFTs
     
  • Pregnancy status if relevant


 

Supporting Information

For Professionals

 

For Patients

 

 

References

 

Page Review Information

Review Date:          12 August 2025
Next Review Date:  12 August 2027
Clinical Editor:         Dr Jack Munro Berry (RMS GP Endocrinology Lead)
Contributors:            Dr Duncan Browne, Consultant Endocrinologist, RCHT