What is the appropriate management of a patient with a thyrotoxic goitre?

Management of Thyrotoxic Goiter

The management of thyrotoxic goiter depends critically on distinguishing between transient destructive thyroiditis (requiring only symptomatic treatment) and true hyperthyroidism from Graves' disease or toxic nodular goiter (requiring definitive therapy with antithyroid drugs, radioactive iodine, or surgery).

Initial Diagnostic Workup

Measure TSH, free T4, and total T3 to confirm thyrotoxicosis (low TSH with elevated free T4 or T3), and assess symptom severity including weight loss, palpitations, heat intolerance, and presence of goiter 1.

Critical Step: Determine if Transient vs. Persistent

• Order radioiodine uptake scan (preferably iodine-123) as the key differentiating test: low or absent uptake indicates destructive thyroiditis (transient), while elevated uptake confirms true hyperthyroidism requiring definitive treatment 1.
• Doppler ultrasound measuring thyroid blood flow serves as an alternative if radioiodine scanning is contraindicated 1.
• Test for TSH receptor antibodies (TRAb or TSI) to identify Graves' disease, and thyroid peroxidase (TPO) antibodies to support autoimmune thyroiditis 1.
• Physical examination findings of ophthalmopathy or thyroid bruit are pathognomonic for Graves' disease and warrant immediate endocrine referral 2.

Management Based on Etiology and Severity

For Transient Thyrotoxicosis (Destructive Thyroiditis)

Beta-blockers (atenolol or propranolol) for symptomatic relief are the mainstay of treatment 2, 1.

• Never initiate thionamides or radioactive iodine for transient thyrotoxicosis, as it is self-limiting and resolves spontaneously within 2-14 weeks 1.
• Monitor thyroid function every 2-3 weeks to document resolution and detect subsequent hypothyroidism, which is the most common outcome 2, 1.
• For mild symptoms (Grade 1): continue beta-blockers with close monitoring 2.
• For moderate symptoms (Grade 2): consider hydration and supportive care, with endocrine consultation if symptoms persist beyond 6 weeks 2.
• For severe symptoms (Grade 3-4): hospitalize for inpatient endocrine consultation, which may guide use of steroids, SSKI, or other medical therapies 2.

For True Hyperthyroidism (Graves' Disease or Toxic Nodular Goiter)

Three definitive treatment options exist: antithyroid drugs, radioactive iodine, or surgery 3, 4.

Antithyroid Drug Therapy

• Methimazole is the preferred thionamide for Graves' disease and toxic multinodular goiter, used either for 12-18 months to induce remission or short-term to achieve euthyroid state before definitive therapy 5, 4.
• Propylthiouracil is reserved for patients intolerant of methimazole 6.
• Antithyroid drugs will not cure toxic nodular goiter, only control hyperthyroidism temporarily 3.

Radioactive Iodine (I-131)

• Radioactive iodine is increasingly used as first-line therapy and resolves hyperthyroidism in >90% of patients with Graves' disease and toxic multinodular goiter 4.
• This is the treatment of choice for toxic nodular goiter 3, 7.
• Contraindicated in pregnancy and lactation; pregnancy should be avoided for 4 months post-treatment 3.
• May worsen Graves' ophthalmopathy; consider corticosteroid cover to reduce this risk 3.
• Hypothyroidism develops in most patients within 1 year, requiring lifelong levothyroxine replacement 4.

Surgery (Thyroidectomy)

• Surgery is the preferred treatment when there are compressive symptoms from an obstructive goiter 4.
• Also indicated for large goiters causing neck compression symptoms, when radioiodine is refused, or for toxic adenoma and toxic multinodular goiter in selected cases 3, 7, 8.
• Subtotal or near-total thyroidectomy aims to cure the pathology while potentially maintaining euthyroidism 3.

Common Pitfalls to Avoid

• Always obtain radioiodine uptake scan or Doppler ultrasound before initiating definitive treatment to avoid inappropriately treating transient thyroiditis with thionamides or radioiodine 1.
• Do not use levothyroxine suppression therapy in patients with suppressed TSH levels, as this risks inducing toxic symptoms 8.
• Recognize that elevated TSH during recovery from thyroiditis may be transient; in asymptomatic patients with normal free T4, monitor for 3-4 weeks before treating 2.