What are the potential causes and treatment options for a patient presenting with a tender thyroid nodule?

Causes of Tender Thyroid Nodule

A tender thyroid nodule is most commonly caused by subacute granulomatous thyroiditis (de Quervain's thyroiditis), hemorrhage into a nodule, or acute suppurative thyroiditis from bacterial infection. 1

Primary Etiologies of Thyroid Nodule Tenderness

Inflammatory Causes

• Subacute granulomatous thyroiditis presents with painful, tender thyroid enlargement, often following a viral upper respiratory infection, and is characterized by systemic symptoms including fever and malaise 1
• Hashimoto's thyroiditis can occasionally cause mild tenderness, though it is typically painless and associated with autoimmune thyroid dysfunction 1
• Acute suppurative thyroiditis from bacterial infection causes severe pain, tenderness, fever, and requires immediate antibiotic therapy and potential drainage 1

Hemorrhagic Complications

• Nodule rupture following thermal ablation procedures presents with neck discomfort, swelling, and reduced echogenicity on ultrasound, with incidences ranging from 0.08% to 0.21% 2
• Spontaneous hemorrhage into a cyst or nodule causes acute pain and rapid enlargement, particularly in larger nodules 2

Iatrogenic Causes

• Post-ablation complications including nodule rupture can cause tenderness, with early symptoms including neck discomfort and swelling alongside reduced echogenicity in the ablation zone 2
• Radiation-induced thyroiditis following external beam radiation or radioactive iodine therapy causes painful inflammation 1

Drug-Induced Thyroiditis

• Medications including amiodarone, interferon-alfa, interleukin-2, or lithium can cause drug-induced thyroiditis with variable degrees of tenderness 1

Diagnostic Approach to Tender Thyroid Nodules

Initial Clinical Assessment

• Determine the presence and severity of pain, tenderness, fever, and systemic symptoms to differentiate between infectious, inflammatory, and hemorrhagic etiologies 1
• Assess thyroid function status (TSH, free T4) as patients may present with euthyroidism, hyperthyroidism, or hypothyroidism depending on the underlying cause 1

Imaging Evaluation

• High-resolution ultrasound should be performed to characterize the nodule, assess for hemorrhage, rupture, or abscess formation, and evaluate surrounding structures 3
• Radioactive iodine uptake is typically reduced in viral, radiation-induced, traumatic, autoimmune, or drug-induced thyroid inflammation 1

Laboratory Testing

• Measure serum TSH and thyroid hormones to determine functional status 1
• Consider serum calcitonin measurement if malignancy is suspected, as it has higher sensitivity than fine-needle aspiration alone for detecting medullary thyroid cancer 3, 4
• Inflammatory markers (ESR, CRP) are elevated in subacute granulomatous thyroiditis 1

Role of Fine-Needle Aspiration

• FNAB is the preferred diagnostic method for thyroid nodules requiring pathological confirmation, but should be deferred in acute inflammatory conditions until inflammation resolves 2, 3
• FNAB is strongly recommended for nodules >1 cm with suspicious features once acute tenderness resolves, to exclude underlying malignancy 3, 4

Treatment Strategies Based on Etiology

Inflammatory Thyroiditis Management

• NSAIDs are the first-line treatment for symptomatic relief of thyroid pain and tenderness in subacute granulomatous thyroiditis 1
• Corticosteroids may be necessary for severe or refractory cases of subacute thyroiditis 1
• Restoration of euthyroidism with thyroid hormone replacement or antithyroid medications as needed based on functional status 1

Hemorrhagic Nodule Management

• Early administration of NSAIDs can improve prognosis in symptomatic nodule rupture following ablation procedures 2
• Analgesia and observation for minor hemorrhage without signs of infection 2
• Incision and drainage may be required depending on severity, particularly if abscess formation occurs 2
• Surgical excision becomes necessary when extensive cellulitis develops 2

Infectious Thyroiditis Management

• Immediate antibiotic therapy for acute suppurative thyroiditis with coverage for common pathogens 1
• Drainage procedures for abscess formation 1

Critical Pitfalls to Avoid

• Do not dismiss tenderness as benign without proper evaluation, as underlying malignancy can coexist with inflammatory conditions 3
• Do not perform FNAB during acute inflammation, as this may worsen symptoms and yield non-diagnostic samples; wait until inflammation subsides 1
• Do not overlook drug-induced thyroiditis in patients taking amiodarone, interferon, interleukin-2, or lithium 1
• Do not assume all tender nodules are inflammatory—hemorrhage into a malignant nodule can occur and requires cytological evaluation once acute symptoms resolve 5

Follow-Up Protocol

• Repeat ultrasound at 4-6 weeks after resolution of acute symptoms to reassess nodule characteristics and determine need for FNAB 3
• Perform FNAB for persistent nodules >1 cm or those with suspicious ultrasound features (solid composition, hypoechogenicity, irregular margins, microcalcifications) once tenderness resolves 3, 4
• Monitor thyroid function during and after treatment, as transient hypothyroidism commonly follows the hyperthyroid phase of subacute thyroiditis 1