What is the initial management for a female patient with a 10-day history of severe neck pain, heat intolerance, palpitations, insomnia, and anxiety, who has a history of viral upper respiratory tract infection 4 weeks ago, presents with sinus tachycardia, a tender normal-sized thyroid gland, low 24-hour radioactive iodine uptake, suppressed Thyroid-Stimulating Hormone (TSH), elevated Triiodothyronine Reverse (RT3), and elevated Thyroxine (T4) free serum levels?

Initial Management: Propranolol for Symptomatic Relief in Subacute Thyroiditis

The initial management for this patient is Propranolol (Option A) to control the symptomatic thyrotoxicosis caused by subacute (viral) thyroiditis. 1, 2

Clinical Diagnosis: Subacute Thyroiditis

This patient presents with the classic triad of subacute thyroiditis:

• Severe neck pain with tender thyroid gland following a viral upper respiratory infection 4 weeks prior 2, 3
• Thyrotoxic symptoms (heat intolerance, palpitations, insomnia, anxiety, tachycardia) with suppressed TSH (<0.01) and elevated free T4 (34 pmol/L) 1, 2
• Low radioactive iodine uptake (5%), which distinguishes this from Graves' disease and confirms destructive thyroiditis with release of preformed hormone 2

The elevated reverse T3 (4.8 mol/L) further supports thyroid inflammation with altered peripheral conversion. 1

Why Propranolol is the Correct Initial Management

Beta blockers are the first-line treatment for the hyperthyroid phase of subacute thyroiditis to control adrenergic symptoms including tachycardia, palpitations, tremor, anxiety, and heat intolerance. 4, 1, 2 The goal is symptomatic relief while the self-limited inflammatory process resolves spontaneously over several weeks to months. 2, 3

Propranolol specifically addresses this patient's most concerning symptoms:

• Sinus tachycardia 4
• Palpitations 1
• Anxiety and insomnia 2
• Heat intolerance 1

Why the Other Options Are Incorrect

B. Levothyroxine - Contraindicated

Levothyroxine would worsen the patient's thyrotoxicosis, as she already has elevated free T4 and suppressed TSH from excessive thyroid hormone release. 5, 1 This is the opposite of what she needs. Levothyroxine is only considered later if she develops the hypothyroid phase after thyroid hormone stores are depleted. 1, 2

C. Methimazole - Ineffective and Inappropriate

Methimazole blocks new thyroid hormone synthesis, but subacute thyroiditis involves release of preformed hormone from damaged follicular cells, not increased synthesis. 1, 2 The low radioactive iodine uptake (5%) confirms the thyroid is not actively producing hormone, making antithyroid drugs completely ineffective. 2 Methimazole would be appropriate for Graves' disease, which presents with high iodine uptake.

D. Radioactive Iodine - Dangerous and Contraindicated

Radioactive iodine ablation is absolutely contraindicated with low iodine uptake, as the thyroid cannot concentrate the isotope. 2 This treatment is reserved for hyperthyroidism with increased hormone production (Graves' disease, toxic nodular goiter), not destructive thyroiditis. 2

Complete Management Algorithm

Immediate Treatment (First 2-8 Weeks)

• Propranolol 40 mg daily (or equivalent beta blocker), titrated to control heart rate and symptoms 4, 1, 2
• NSAIDs or aspirin for thyroid pain and inflammation 1, 2, 3
• Prednisone 40 mg daily if pain is severe or unresponsive to NSAIDs, with gradual taper over several weeks 3

Monitoring Phase (Weeks to Months)

• Surveillance of thyroid function every 4-6 weeks to detect transition to hypothyroid phase 1, 2
• Most patients progress through: thyrotoxicosis → hypothyroidism → euthyroidism 1, 2
• The hypothyroid phase typically occurs 2-6 months after symptom onset 1

Hypothyroid Phase Management (If Occurs)

• Levothyroxine therapy if TSH >10 mIU/L or symptomatic hypothyroidism develops 5, 1
• Most cases are transient; attempt to discontinue levothyroxine after 6-12 months 1, 2
• Less than 1% develop permanent hypothyroidism requiring lifelong replacement 3

Critical Pitfalls to Avoid

Never start antithyroid drugs (methimazole) based solely on elevated thyroid hormones without confirming the mechanism. 2 The radioactive iodine uptake scan is essential to distinguish destructive thyroiditis (low uptake) from hyperthyroidism with increased synthesis (high uptake). 2

Do not miss the time-lag phenomenon: In 18.5% of subacute thyroiditis cases, laboratory findings may be normal at initial presentation despite classic symptoms, with TSH suppression appearing up to 11 weeks after symptom onset. 6 If clinical suspicion is high but initial labs are normal, repeat testing in 2-4 weeks. 6

Distinguish subacute thyroiditis from painful Hashimoto's exacerbation: Both can present with painful thyroid and thyrotoxicosis, but Hashimoto's patients typically have pre-existing goiter, high antimicrosomal antibodies, and 62.5% develop permanent hypothyroidism (versus <1% in subacute thyroiditis). 7 This patient's lack of prior goiter history and viral prodrome favor subacute thyroiditis. 2, 3