Evaluation and Management of Suspected Thyroiditis
For suspected thyroiditis, immediately measure TSH and free T4 to determine the phase of disease, then provide conservative management during the thyrotoxic phase with beta blockers for symptoms, followed by levothyroxine replacement once hypothyroidism develops.
Initial Diagnostic Approach
Measure TSH and free T4 as the first-line tests to establish whether the patient is in the thyrotoxic, hypothyroid, or euthyroid phase of thyroiditis 1, 2. Most forms of thyroiditis follow a triphasic pattern: initial thyrotoxicosis from release of preformed hormone, followed by hypothyroidism as stores deplete, then eventual recovery (though some develop permanent hypothyroidism) 1, 2.
Key Clinical Features to Identify
- Thyrotoxic phase: High free T4 or T3 with low/normal TSH, often asymptomatic but may have weight loss, palpitations, heat intolerance, tremors, anxiety, or diarrhea 3
- Hypothyroid phase: High TSH with low free T4, presenting with fatigue, weight gain, cold intolerance, constipation 4
- Neck pain: Suggests subacute thyroiditis specifically, characterized by anterior neck tenderness 1, 2, 5
- Painless presentation: Most common in immune checkpoint inhibitor-induced or postpartum thyroiditis 3
Additional Diagnostic Tests
Order thyroid peroxidase (TPO) antibodies to identify autoimmune etiology (Hashimoto thyroiditis), which predicts higher progression risk to permanent hypothyroidism (4.3% per year vs 2.6% in antibody-negative patients) 4, 1.
Consider thyroid stimulating immunoglobulin (TSI) or TSH receptor antibody (TRAb) if Graves' disease needs to be excluded, though this is rare with thyroiditis 3.
Obtain radioactive iodine uptake scan (RAIUS) or Technetium-99m scan when feasible to distinguish thyroiditis (low uptake) from Graves' disease (high uptake) 3. Doppler ultrasound can also differentiate thyrotoxicosis (increased blood flow) from destructive thyroiditis (decreased blood flow) 4.
Management by Phase
Thyrotoxic Phase Management
Conservative management is sufficient during the thyrotoxic phase of thyroiditis, as this is a self-limiting process 3.
- Prescribe non-selective beta blockers (preferably with alpha receptor-blocking capacity) for symptomatic patients with palpitations, tremor, or anxiety 3, 1
- Do NOT use antithyroid drugs (methimazole, propylthiouracil), as the thyrotoxicosis results from hormone release, not overproduction 1, 2
- Repeat thyroid function tests every 2-3 weeks to monitor for transition to hypothyroidism 3
For subacute thyroiditis with significant neck pain, treat with NSAIDs first; if inadequate relief, escalate to corticosteroids (prednisone 40mg daily) 1, 2, 5.
Hypothyroid Phase Management
Initiate levothyroxine when TSH becomes elevated and free T4 drops, which typically occurs an average of 1 month after the thyrotoxic phase and 2 months from thyroiditis onset 3.
Dosing strategy:
- For patients <70 years without cardiac disease: Start with full replacement dose of approximately 1.6 mcg/kg/day 6, 4
- For patients >70 years or with cardiac disease: Start with 25-50 mcg/day and titrate gradually 6, 4
Monitor TSH every 6-8 weeks during dose titration, targeting TSH within the reference range (0.5-4.5 mIU/L) 6.
Critical Safety Consideration
Before initiating levothyroxine, rule out concurrent adrenal insufficiency, especially in patients with suspected central hypothyroidism or hypophysitis, as starting thyroid hormone before corticosteroids can precipitate life-threatening adrenal crisis 6, 4. If adrenal insufficiency is present, start physiologic dose steroids 1 week prior to thyroid hormone replacement 4.
Specific Thyroiditis Subtypes
Hashimoto Thyroiditis
- Presents with painless goiter and elevated TPO antibodies 1, 2
- Treat with lifelong levothyroxine if overt hypothyroidism develops 1
- Consider treatment even for subclinical hypothyroidism (TSH 4.5-10 mIU/L with normal free T4) if symptomatic or TPO antibody-positive 4
Postpartum Thyroiditis
- Occurs within one year of delivery, miscarriage, or medical abortion 1, 2
- Initial hyperthyroid phase may be mistaken for postpartum depression 4
- Monitor for permanent hypothyroidism, which develops in a subset of patients 4, 1
- Treat hypothyroid phase with levothyroxine if TSH >10 mIU/L or if TSH 4-10 mIU/L with symptoms or fertility concerns 2
Subacute Thyroiditis
- Characterized by anterior neck pain and tenderness, often following upper respiratory viral illness 1, 2, 5
- Treat pain with NSAIDs or corticosteroids 1, 2, 5
- Most cases resolve spontaneously within several months 2
- Hypothyroid phase treatment generally not necessary unless symptomatic or permanent hypothyroidism develops 1
Drug-Induced Thyroiditis
Immune checkpoint inhibitors (anti-PD-1/PD-L1, anti-CTLA-4) cause thyroid dysfunction in 6-20% of patients 3.
- Continue immunotherapy in most cases, as thyroid dysfunction rarely requires treatment interruption 3
- Monitor TSH every 4-6 weeks for the first 3 months, then every second cycle 3
- Consider levothyroxine even for subclinical hypothyroidism if fatigue or other symptoms present 4
Other drugs that may induce thyroiditis include amiodarone, interleukin-2, interferon-alfa, lithium, and tyrosine kinase inhibitors 1.
Surveillance and Follow-Up
Regular monitoring every 6-12 months is recommended for patients with positive thyroid antibodies to detect progression to permanent hypothyroidism 4.
Recheck thyroid function after resolution of acute illness or medication changes, as these can transiently affect thyroid tests 4.
Once on stable levothyroxine therapy, repeat TSH every 6-12 months or sooner if symptoms change 6.
Common Pitfalls to Avoid
Do not treat based on a single elevated TSH value, as 30-60% normalize on repeat testing 6. Confirm with repeat measurement after 3-6 weeks 6.
Never start thyroid hormone before ruling out adrenal insufficiency in suspected central hypothyroidism or hypophysitis—this can precipitate adrenal crisis 6, 4.
Avoid antithyroid drugs during the thyrotoxic phase of thyroiditis, as the mechanism is hormone release, not overproduction 1, 2.
Do not assume hypothyroidism is permanent without reassessment, as many patients recover normal thyroid function after thyroiditis 6.
Approximately 25% of patients on levothyroxine are unintentionally overtreated with TSH fully suppressed, increasing risks for atrial fibrillation, osteoporosis, and fractures 6. Monitor carefully to avoid overtreatment.
When to Refer to Endocrinology
An endocrinology consultation is recommended in all cases of suspected or confirmed thyroiditis, particularly when there is diagnostic uncertainty, difficulty managing thyroid hormone replacement, or concern for other endocrinopathies 3.