What is the stepwise management of a patient with suspected thyroiditis?

Stepwise Management of Suspected Thyroiditis

The initial step in managing suspected thyroiditis is to measure TSH and free T4 to determine the phase of thyroid dysfunction, followed by targeted symptom management with beta blockers for thyrotoxic symptoms and monitoring for progression to hypothyroidism. 1

Step 1: Initial Clinical Assessment and Laboratory Evaluation

Obtain baseline thyroid function tests immediately:

• Measure TSH and free T4 (or total T3) to determine current thyroid status 1
• Most patients with thyroiditis present with asymptomatic (painless) thyroiditis showing high free T4 or T3 levels with low/normal TSH 1
• The thyrotoxic phase occurs an average of one month after immunotherapy initiation in drug-induced cases 1

Assess for clinical symptoms:

• Thyrotoxicosis may present with weight loss, palpitations, heat intolerance, tremors, anxiety, diarrhea, and hypermetabolic symptoms, though these may be masked by beta blockers 1
• Subacute thyroiditis characteristically presents with anterior neck pain and tenderness over the thyroid gland 2, 3, 4
• Hashimoto thyroiditis typically presents with a painless goiter and symptoms of hypothyroidism 2, 3
• Fatigue can be a presenting symptom even in the thyrotoxic phase, despite seeming counterintuitive 5

Step 2: Differentiate Thyroiditis from Other Causes of Thyrotoxicosis

Order additional diagnostic tests when thyroiditis is suspected:

• Measure thyroid stimulating hormone receptor antibody (TRAb) or thyroid stimulating immunoglobulin (TSI) to rule out Graves' disease 1
• Check thyroid peroxidase (TPO) antibody levels, particularly for Hashimoto thyroiditis 1, 2, 3
• Consider radioactive iodine uptake scan (RAIUS) or Technetium-99m pertechnetate thyroid scan if recent iodinated contrast was not used 1
• Thyroiditis shows low radioactive iodine uptake, distinguishing it from Graves' disease which shows high uptake 3, 6

Key distinguishing features:

• Thyroiditis is the most frequent cause of thyrotoxicosis with immune checkpoint inhibitors, occurring more commonly with anti-PD1/PD-L1 drugs than anti-CTLA-4 agents 1
• Graves' disease is very rare and occurs more commonly with anti-CTLA-4 drugs 1
• Subacute granulomatous thyroiditis often follows an upper respiratory viral illness 3

Step 3: Manage the Thyrotoxic Phase (If Present)

Conservative management is sufficient during the thyrotoxic phase:

• Thyroiditis is a self-limiting process requiring only symptomatic treatment 1
• Do not use antithyroid medications (methimazole or propylthiouracil), as thyrotoxicosis results from hormone release, not overproduction 2, 3

Provide symptomatic relief:

• Prescribe non-selective beta blockers, preferably with alpha receptor-blocking capacity, for symptomatic patients with palpitations, tremors, or anxiety 1
• For subacute thyroiditis with neck pain, use nonsteroidal anti-inflammatory drugs (NSAIDs) as first-line therapy 2, 3
• If NSAIDs provide inadequate pain relief, escalate to corticosteroids (prednisone 40mg daily) 2, 4
• High-dose acetylsalicylic acid is an alternative for thyroid pain relief 3

Step 4: Monitor for Progression to Hypothyroidism

Establish a monitoring schedule:

• Repeat thyroid hormone levels (TSH and free T4) every 2-3 weeks during the thyrotoxic phase 1
• The thyrotoxic phase typically lasts approximately one month 1
• Hypothyroidism develops an average of 1 month after the thyrotoxic phase and 2 months from immunotherapy initiation 1

Watch for clinical signs of hypothyroidism:

• Unexplained fatigue, weight gain, hair loss, cold intolerance, constipation, and depression indicate progression to hypothyroidism 1
• Lab tests showing high TSH and low free T4 confirm biochemical hypothyroidism 1

Step 5: Initiate Thyroid Hormone Replacement When Hypothyroidism Develops

Start levothyroxine at the time of hypothyroidism diagnosis:

• For patients <70 years without cardiac disease, start with full replacement dose of approximately 1.6 mcg/kg/day 7
• For patients >70 years or with cardiac disease/multiple comorbidities, start with lower dose of 25-50 mcg/day and titrate gradually 7
• Thyroiditis leads to permanent hypothyroidism in most cases, requiring lifelong thyroid hormone replacement 1, 2

Critical safety consideration:

• Before initiating levothyroxine, rule out concurrent adrenal insufficiency, as starting thyroid hormone before corticosteroids can precipitate adrenal crisis 1, 7
• In patients with suspected central hypothyroidism or hypophysitis, always start physiologic dose steroids 1 week prior to thyroid hormone replacement 7

Step 6: Refer to Endocrinology

Endocrinology consultation is recommended in all cases of suspected or confirmed thyroiditis:

• Referral ensures appropriate management of the evolving thyroid dysfunction 1
• Specialist input is particularly important for drug-induced thyroiditis in patients on immunotherapy 1
• Continue immune checkpoint inhibitor therapy in most cases, as thyroid dysfunction rarely requires treatment interruption 7

Common Pitfalls to Avoid

Do not treat thyroiditis-induced thyrotoxicosis with antithyroid drugs:

• The thyrotoxicosis results from release of preformed hormone, not hormone overproduction 2, 3
• Antithyroid medications are ineffective and unnecessary 2, 3

Do not delay monitoring for hypothyroidism:

• Approximately 30-60% of patients with transient thyrotoxicosis will develop permanent hypothyroidism 7
• Missing the transition to hypothyroidism can result in prolonged symptomatic hypothyroidism 1

Do not assume all thyroid pain is thyroiditis:

• Acute suppurative thyroiditis (bacterial infection) requires antibiotic treatment, not NSAIDs alone 6, 8
• Invasive fibrous thyroiditis (Riedel's struma) can mimic carcinoma and requires different management 8

Do not start levothyroxine before ruling out adrenal insufficiency:

• This can precipitate life-threatening adrenal crisis in patients with concurrent hypophysitis 1, 7
• Always check morning cortisol if fatigue is severe or if central hypothyroidism is suspected 5