What is the further workup for suspected thyroiditis?

Workup for Suspected Thyroiditis

The diagnostic workup for suspected thyroiditis should include thyroid function tests (TSH, Free T4, and Free T3 if indicated), thyroid peroxidase (TPO) antibodies, and clinical evaluation of symptoms to determine the specific type of thyroiditis and guide appropriate management. 1, 2

Initial Laboratory Assessment

• Thyroid Function Tests:

  • TSH, Free T4 (essential)
  • Free T3 (if hyperthyroidism is suspected)
  • Interpretation guidelines:
    • Low TSH (<0.45 mIU/L) suggests hyperthyroidism
    • Very low TSH (<0.1 mIU/L) strongly indicates hyperthyroidism
    • Elevated TSH with low T4 indicates hypothyroidism 1

• Thyroid Antibodies:

  • Thyroid peroxidase (TPO) antibodies - particularly important for confirming autoimmune etiology in Hashimoto's thyroiditis 1, 2
  • Thyroglobulin antibodies - may provide additional confirmation of autoimmune thyroiditis

• Inflammatory Markers:

  • ESR (erythrocyte sedimentation rate) and CRP (C-reactive protein) - particularly elevated in subacute thyroiditis 2

Imaging Studies

• Thyroid Ultrasound:

  • Evaluate for characteristic patterns of different thyroiditis types
  • Assess for nodules, diffuse enlargement, or heterogeneous echotexture
  • Helps differentiate between different forms of thyroiditis 2, 3

• Radioactive Iodine Uptake (RAIU):

  • Low uptake is characteristic of thyroiditis (differentiates from Graves' disease)
  • Most forms of thyroiditis result in reduced radioactive iodine uptake due to inflammation 2, 3

Differential Diagnosis Based on Clinical Presentation

Hashimoto's Thyroiditis

• Painless goiter
• Elevated TPO antibodies
• Often presents with hypothyroidism
• Requires lifelong thyroid hormone therapy if hypothyroid 2

Subacute (Granulomatous) Thyroiditis

• Anterior neck pain is characteristic
• Often follows upper respiratory viral illness
• Triphasic pattern: hyperthyroidism → hypothyroidism → recovery
• Self-limited in most cases 2, 3

Postpartum Thyroiditis

• Occurs within one year of delivery, miscarriage, or abortion
• Often presents with initial hyperthyroidism followed by hypothyroidism
• Monitor thyroid function every 2-3 weeks to detect transition to hypothyroidism 1, 3

Drug-Induced Thyroiditis

• Check medication history for:
  • Amiodarone
  • Immune checkpoint inhibitors
  • Interleukin-2
  • Interferon-alfa
  • Lithium
  • Tyrosine kinase inhibitors 2

Monitoring and Follow-up

• For subclinical hyperthyroidism:

  TSH Level	Monitoring Frequency
  0.1-0.45 mIU/L	Every 3 months
  <0.1 mIU/L	Every 4-6 weeks

• For patients with thyroiditis, regular monitoring is essential to detect changes in thyroid function, especially transition from hyperthyroid to hypothyroid phase 1, 2

Treatment Considerations

• Hyperthyroid phase:

  • Beta-blockers for symptomatic relief
  • NSAIDs for pain in subacute thyroiditis
  • Corticosteroids for severe thyroid pain 2, 3

• Hypothyroid phase:

  • Levothyroxine therapy if TSH >10 mIU/L
  • Consider treatment if TSH 4-10 mIU/L with symptoms 1, 3

• Special populations:

  • Pregnant women require more frequent monitoring and dose adjustments
  • Postpartum women should be monitored for thyroiditis, especially those with history of thyroid disorders 1

Remember that most forms of thyroiditis follow a triphasic pattern (hyperthyroidism → hypothyroidism → recovery), but some patients may develop permanent hypothyroidism requiring lifelong therapy 2, 3.