Hyperthyroidism and Graves' Disease: Diagnosis and Treatment

Hyperthyroidism is an overactive thyroid gland producing too much thyroid hormone. The resulting state, thyrotoxicosis, speeds up the body's metabolism. It is more common in women and can cause serious heart problems if untreated.

Causes

• Graves' disease — the most common cause. It is autoimmune: TSH receptor antibodies stimulate the thyroid.
• Toxic multinodular goitre — common in older people and in iodine-deficient areas.
• Toxic adenoma — a single overactive nodule.
• Thyroiditis (subacute, painless or postpartum) — causes temporary thyrotoxicosis from hormone leakage, often followed by hypothyroidism.
• Drugs: amiodarone, excess levothyroxine, iodine.

Clinical features

Symptoms:

• weight loss despite a good appetite
• heat intolerance and sweating
• palpitations
• tremor
• anxiety and irritability
• diarrhoea
• light or absent periods
• muscle weakness

Signs:

• tachycardia or atrial fibrillation
• fine tremor
• warm, moist skin
• lid lag
• goitre

Features specific to Graves' disease:

• a diffuse goitre, sometimes with a bruit
• thyroid eye disease: exophthalmos, lid retraction, eye irritation, double vision
• pretibial myxoedema
• thyroid acropachy

Investigations

• Suppressed (low) TSH, with raised free T4 and/or free T3.
• TSH receptor antibodies (TRAb): confirm Graves' disease.
• Thyroid uptake scan: distinguishes the causes. Uptake is diffuse and high in Graves', patchy in multinodular goitre, a single "hot" nodule in toxic adenoma, and low in thyroiditis.
• ECG: sinus tachycardia or atrial fibrillation.

Treatment

• Beta-blockers (for example propranolol) for rapid symptom relief, unless contraindicated.
• Antithyroid drugs:
  • Carbimazole or methimazole are usually first-line.
  • Propylthiouracil is preferred in the first trimester of pregnancy and in thyroid storm, but carries a risk of severe liver injury.
• Radioactive iodine: a common definitive treatment. It is contraindicated in pregnancy and breastfeeding, and can worsen active thyroid eye disease.
• Surgery (thyroidectomy) for large goitres, compressive symptoms, suspicion of cancer, or patient choice.
• Thyroiditis usually needs only symptomatic treatment, because antithyroid drugs do not help.

Important side effect: agranulocytosis

Antithyroid drugs can rarely cause agranulocytosis, a dangerous fall in white cells. Patients must be told to stop the drug and get an urgent full blood count if they develop a sore throat, mouth ulcers or fever.

Thyroid storm

A life-threatening emergency, usually triggered by infection, surgery or stopping treatment. Features:

• high fever
• severe tachycardia or atrial fibrillation
• heart failure
• agitation, delirium or coma
• vomiting and diarrhoea
• jaundice

It needs intensive care with:

• beta-blockers
• high-dose antithyroid drugs (often propylthiouracil)
• iodine solution, given after the antithyroid drug
• corticosteroids
• supportive care

Exam pearls

• Exophthalmos and pretibial myxoedema point to Graves' disease specifically.
• Any patient on carbimazole with a sore throat needs an urgent white cell count.
• New atrial fibrillation: always check thyroid function.

See also Hypothyroidism, Atrial Fibrillation and the Medicine Companion.

Test yourself

5 exam-style single-best-answer questions. Choose your answer, then tap “Show answer”.

1. Which feature is specific to Graves' disease?

   1. Tachycardia
   2. Weight loss
   3. Heat intolerance
   4. Tremor
   5. Exophthalmos
   Show answer

   Answer: E. Exophthalmos
   Thyroid eye disease (exophthalmos) and pretibial myxoedema are specific to Graves' disease.

2. A patient on carbimazole develops a sore throat and fever. What should be done?

   1. Continue and give lozenges
   2. Stop the drug and check an urgent full blood count
   3. Double the dose
   4. Start antibiotics only
   5. Ignore
   Show answer

   Answer: B. Stop the drug and check an urgent full blood count
   Agranulocytosis is a rare but serious side effect; check neutrophils urgently.

3. Preferred antithyroid drug in the first trimester of pregnancy:

   1. Carbimazole
   2. Propylthiouracil
   3. Radioactive iodine
   4. Lithium
   5. Levothyroxine
   Show answer

   Answer: B. Propylthiouracil
   Propylthiouracil is preferred in the first trimester because carbimazole/methimazole carry embryopathy risk.

4. Thyrotoxicosis with low uptake on a thyroid scan suggests:

   1. Toxic adenoma
   2. TSH-secreting adenoma
   3. Toxic multinodular goitre
   4. Graves' disease
   5. Thyroiditis
   Show answer

   Answer: E. Thyroiditis
   Thyroiditis causes hormone leakage with low uptake; antithyroid drugs do not help.

5. Which drug gives rapid symptom relief in thyrotoxicosis?

   1. Levothyroxine
   2. Metformin
   3. Furosemide
   4. Propranolol
   5. Amlodipine
   Show answer

   Answer: D. Propranolol
   Beta-blockers rapidly control tremor, palpitations and anxiety while definitive treatment takes effect.

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Disclaimer

For education and exam preparation only. This is not medical advice and must not be used to diagnose or treat patients. Always follow current clinical guidelines and the advice of qualified senior colleagues.