Subacute thyroiditis (de Quervain) is one of those “classic vignette” thyroid disorders that shows up on Step exams because it’s pattern recognition gold: a recent viral illness → painful thyroid → transient hyperthyroidism → then hypothyroidism → then recovery. If you can quickly distinguish it from painless/postpartum thyroiditis and Graves disease, you’ll grab easy points.
Where it fits in Step thyroid world (big picture)
Think of thyroid disorders in two buckets:
- Increased hormone production (e.g., Graves, toxic multinodular goiter) → thyroid is making more hormone
- Release of preformed hormone due to gland damage (thyroiditis) → thyroid is leaking hormone
Subacute thyroiditis (de Quervain) is the high-yield prototype of the second bucket: painful, post-viral, granulomatous inflammation causing leakage of stored T3/T4.
First Aid cross-reference (conceptual): Endocrine → Thyroid disorders → Thyroiditis vs Graves (focus on painful thyroiditis + low uptake on scan).
Definition (what it is)
Subacute thyroiditis (de Quervain thyroiditis) is a self-limited inflammatory thyroid disease typically occurring after a viral upper respiratory infection, characterized by:
- Painful, tender thyroid (often radiating to jaw/ear)
- Transient hyperthyroid phase from release of preformed hormone
- Followed by hypothyroid phase
- Usually returns to euthyroid state within weeks to months
Pathophysiology (why it happens)
Core mechanism: “leak” not “overproduction”
Inflammation damages thyroid follicles → stored thyroglobulin with T3/T4 leaks into circulation.
Key implications:
- TSH is suppressed during the hyperthyroid phase (negative feedback)
- New hormone synthesis is low, so:
- Radioactive iodine uptake (RAIU) is low
- Antithyroid synthesis blockers (methimazole/PTU) generally don’t help
Histology (high-yield buzzwords)
- Granulomatous inflammation
- Multinucleated giant cells
- Disrupted follicles with inflammatory infiltrate
If a question gives you granulomas + painful thyroid after viral illness, de Quervain should be at the top.
Classic clinical presentation (what you’re supposed to recognize)
The vignette you’re likely to see
- Recent viral URI (sore throat, malaise, myalgias)
- Anterior neck pain and thyroid tenderness
- Pain may radiate to jaw or ear
- Fever and fatigue are common
Thyroid status evolves over time (testable sequence)
Triphasic course:
- Hyperthyroid phase (days–weeks)
- Palpitations, tremor, heat intolerance, anxiety
- Painful thyroid helps differentiate from Graves
- Hypothyroid phase (weeks)
- Fatigue, cold intolerance, constipation
- Recovery (most return to euthyroid)
Step trick: symptoms can “flip” over time—don’t get anchored on the initial labs.
Diagnosis (what labs and imaging show)
High-yield lab pattern (hyperthyroid phase)
| Test | Expected finding | Why |
|---|---|---|
| TSH | Low | negative feedback from high T3/T4 |
| Free T4 / T3 | High (early) | leakage of preformed hormone |
| ESR / CRP | High | inflammatory thyroiditis |
| Thyroglobulin | High | follicular destruction releases it |
| TSI (Graves antibody) | Negative | not Graves |
ESR elevation is a classic clue and frequently tested.
Radioactive iodine uptake (RAIU)
- Low uptake in subacute thyroiditis
Because the gland is inflamed and not synthesizing new hormone.
Compare to Graves:
- Graves = high uptake (diffuse) because synthesis is increased
Ultrasound (when used)
Not always necessary for Step-style diagnosis, but typical pattern:
- Heterogeneous hypoechoic thyroid
- Reduced vascularity compared with Graves (Graves has increased flow, “thyroid inferno”)
Treatment (what you do, and what you don’t do)
Because the hyperthyroidism is from release, not increased synthesis:
Symptom control (hyperthyroid phase)
- Beta-blocker (e.g., propranolol) for tremor/palpitations
Pain/inflammation control (key management)
- NSAIDs first-line for pain
- If severe pain or refractory:
- Glucocorticoids (e.g., prednisone)
Hypothyroid phase
- Usually transient; observe if mild
- Levothyroxine can be used temporarily if symptomatic or prolonged hypothyroidism
What not to do (classic Step pitfall)
- Thionamides (methimazole/PTU) generally not effective
(They block synthesis, but the problem is hormone leakage.)
High-yield associations and differentiators (Step 1/2 favorites)
Must-know differentiator table
| Condition | Painful thyroid? | Typical trigger | RAIU | Antibodies | Key clue |
|---|---|---|---|---|---|
| Subacute thyroiditis (de Quervain) | Yes | Post-viral | Low | Usually negative | High ESR, tender thyroid |
| Painless/postpartum thyroiditis | No | Postpartum / autoimmune | Low | Often anti-TPO+ | Painless, postpartum timing |
| Graves disease | No | Autoimmune | High (diffuse) | TSI+ | Ophthalmopathy, pretibial myxedema |
| Hashimoto thyroiditis | Usually no (may be firm) | Autoimmune | Variable | Anti-TPO+, anti-Tg+ | Hypothyroid, lymphoma risk |
| Acute suppurative thyroiditis | Yes | Bacterial | Variable | — | High fever, very sick, focal abscess |
Extra HY pearls
- ESR elevated is disproportionately emphasized for de Quervain.
- No exophthalmos (helps rule out Graves).
- Thyroid may feel enlarged and exquisitely tender.
- Most patients recover; a minority can develop persistent hypothyroidism (test writers may ask about follow-up).
“First Aid-style” memory hooks (without fluff)
- de Quervain = painful + granulomas + giant cells + post-viral
- Thyroiditis hyperthyroidism = low uptake
- Treat pain (NSAIDs/steroids) + control adrenergic symptoms (beta-blocker)
Rapid-fire question stems (practice pattern recognition)
If you see…
- “Neck pain after a viral illness, high ESR, low TSH, high T4” → Subacute thyroiditis
- “Hyperthyroid symptoms + low RAIU + postpartum + painless thyroid” → Postpartum thyroiditis
- “Hyperthyroid + diffusely increased uptake + eye findings” → Graves
Step-ready takeaway
Subacute thyroiditis (de Quervain) is a post-viral, painful, granulomatous thyroiditis with high ESR and a low RAIU hyperthyroid phase due to release of preformed hormone. Manage with NSAIDs (or steroids if severe) and beta-blockers for symptoms; thionamides won’t help because synthesis isn’t the problem.