What are the diagnostic criteria and treatment options for thyroiditis?

Thyroiditis Diagnosis and Treatment

Diagnose thyroiditis using TSH and free T4 levels combined with clinical presentation, then tailor treatment to the specific phase and severity of disease—most cases are self-limited and require only symptomatic management with beta blockers and monitoring, while hypothyroidism requires levothyroxine replacement. 1, 2

Diagnostic Approach

Initial Laboratory Workup

Measure TSH and free T4 as the primary diagnostic tests in all patients with suspected thyroiditis. 1

• Add T3 measurement in highly symptomatic patients with minimal FT4 elevations to capture the full extent of thyrotoxicosis 1
• Check thyroid peroxidase (TPO) antibodies when Hashimoto thyroiditis is suspected (painless goiter with hypothyroidism) 2, 3
• Obtain TSH receptor antibodies if clinical features suggest Graves' disease (ophthalmopathy, thyroid bruit, or T3 toxicosis) 1

Clinical Patterns to Recognize

Thyrotoxicosis (low TSH with elevated FT4/T3): Most commonly represents the initial hyperthyroid phase of subacute thyroiditis, where preformed thyroid hormone is released from damaged follicles 1, 2

Hypothyroidism (elevated TSH with low FT4): Can occur as the second phase after thyroid stores are depleted, or as the primary presentation in Hashimoto thyroiditis 2, 3

Central hypothyroidism (low TSH with low FT4): Indicates pituitary involvement (hypophysitis) rather than primary thyroid disease—requires evaluation for other pituitary hormone deficiencies 1

Distinguishing Subacute Thyroiditis from Other Causes

Anterior neck pain with thyroid tenderness is pathognomonic for subacute granulomatous thyroiditis and distinguishes it from painless (lymphocytic) thyroiditis 2, 3, 4

• Subacute thyroiditis typically follows an upper respiratory viral illness and presents with fever, elevated inflammatory markers, and anterior neck pain 3, 4
• Postpartum thyroiditis occurs within one year of delivery, miscarriage, or medical abortion and is usually painless 1, 2, 3
• Drug-induced thyroiditis should be considered in patients on immune checkpoint inhibitors, amiodarone, interferon-alfa, interleukin-2, lithium, or tyrosine kinase inhibitors 2, 5

Treatment Algorithm

Thyrotoxic Phase Management

Grade 1 (Asymptomatic or Mild Symptoms)

Initiate beta blockers (atenolol or propranolol) for symptomatic relief of palpitations, tremors, and adrenergic symptoms. 1, 6, 2

• Monitor thyroid function every 2-3 weeks to detect transition to hypothyroidism, which occurs in most patients 1, 6
• Continue monitoring without treatment if the patient remains asymptomatic with normal FT4 1
• Refer to endocrinology if thyrotoxicosis persists beyond 6 weeks for additional workup 1, 6

Grade 2 (Moderate Symptoms, Able to Perform ADL)

Provide beta blockers, hydration, and supportive care. 1

• Consider holding immune checkpoint inhibitors (if applicable) until symptoms return to baseline 1
• Refer to endocrinology for persistent thyrotoxicosis beyond 6 weeks for possible medical thyroid suppression 1

Grade 3-4 (Severe Symptoms or Life-Threatening)

Hold immune checkpoint inhibitors immediately and obtain urgent endocrine consultation. 1

• Hospitalize patients with severe symptoms for inpatient management 1
• Administer beta blockers, hydration, and supportive care 1
• Consider additional therapies including steroids, SSKI, or thionamides (methimazole or propylthiouracil) under endocrine guidance 1

Pain Management in Subacute Thyroiditis

Use NSAIDs as first-line therapy for thyroid pain and tenderness. 2, 3

• Escalate to systemic glucocorticoids (prednisone 40mg daily) for severe pain or inadequate response to NSAIDs 6, 4
• Do not continue NSAID monotherapy beyond 1 month if fever persists—this indicates need for glucocorticoids 6

Hypothyroid Phase Management

When to Treat

Initiate levothyroxine for symptomatic hypothyroidism or TSH >10 mIU/L. 3

• In asymptomatic patients with elevated TSH but normal FT4 (subclinical hypothyroidism), monitor for 3-4 weeks before treating to determine if spontaneous recovery occurs 1
• Treat TSH 4-10 mIU/L in symptomatic patients or those desiring fertility 3

Levothyroxine Dosing

For patients under 70 years without cardiac disease or frailty, start full replacement at approximately 1.6 mcg/kg/day based on ideal body weight. 1

For patients over 70 years or with cardiac disease/multiple comorbidities, start with 25-50 mcg daily and titrate upward. 1

• Recheck TSH every 4-6 weeks and adjust dose to maintain TSH in normal range 1
• If TSH becomes suppressed on therapy, reduce or discontinue levothyroxine as this suggests overtreatment or recovery of thyroid function 1

Special Considerations

Thyroiditis is self-limited—the initial hyperthyroidism typically resolves within weeks, most commonly progressing to hypothyroidism. 1

Levothyroxine is NOT indicated during the recovery phase of subacute thyroiditis unless persistent hypothyroidism develops 7

Physical examination findings of ophthalmopathy or thyroid bruit are diagnostic of Graves' disease (not thyroiditis) and require early endocrine referral for definitive treatment with antithyroid drugs, radioactive iodine, or surgery 1

Critical Pitfalls to Avoid

Never start thyroid hormone replacement before administering hydrocortisone in patients with possible central hypothyroidism—this can precipitate adrenal crisis 1

Do not treat thyroid storm empirically without checking thyroid function tests, but do not delay treatment waiting for results if clinical suspicion is high (fever, tachycardia disproportionate to fever, altered mental status) 1

Recognize that postpartum thyroiditis requires different monitoring—TSH and FT4 should be evaluated in women who develop goiter or symptoms of thyroid dysfunction within one year of delivery 1