Thyroiditis: Types, Thyroid and Systemic Effects, and Clinical Management

Thyroiditis encompasses heterogeneous disorders causing thyroid inflammation. The pattern of tissue involvement and clinical course vary by type.

Primary Target: Thyroid Gland

• Follicular destruction → release of preformed hormone → transient thyrotoxicosis.
• Subsequent hypothyroidism if destruction exceeds regenerative capacity.
• Painful (subacute, infectious) vs. painless (Hashimoto's, postpartum, silent).

Perithyroid Tissues

• Strap muscles, recurrent laryngeal nerves, esophagus, trachea → pain, dysphagia, hoarseness, dyspnea.
• Cervical lymphadenopathy (reactive hyperplasia).

Systemic/Remote Effects

• Cardiac: Thyrotoxicosis → tachycardia, AF, high-output failure.
• Bone: Excess thyroid hormone → accelerated turnover → osteoporosis.
• Liver: Altered metabolism, elevated transaminases.
• Hematologic: Anemia of chronic disease, rare aplastic anemia (drug-induced).

Major Types

Type	Etiology	Course
Hashimoto's	Autoimmune (TPO/Tg antibodies)	Chronic → hypothyroidism
Subacute (de Quervain)	Post-viral (granulomatous)	Thyrotoxic → hypo → recovery (90%)
Postpartum	Autoimmune rebound	Thyrotoxic (1–4 mo PP) → hypo (4–8 mo) → recovery (80%)
Silent/Painless	Autoimmune (lymphocytic)	Similar to postpartum, not pregnancy-related
Acute/Suppurative	Bacterial (rare)	Abscess formation; surgical drainage + antibiotics
Drug-induced	Amiodarone, lithium, checkpoint inhibitors, TKIs	Variable

Management

• Thyrotoxic symptoms: β-blockers.
• Hypothyroidism: levothyroxine.
• Pain: NSAIDs, glucocorticoids (subacute).
• Address underlying cause (discontinue offending drug, treat infection).

Thyroiditis is not one disease—it's a spectrum. Accurate typing guides prognosis and therapy.