Thyroiditis

Sub-section: Thyroid Section: Endocrine

Definition

• Inflammation of the thyroid
• Common causes
  • Hashimoto thyroiditis
  • Acute suppurative thyroiditis
  • Subacute thyroiditis
  • Riedel Struma thyroiditis

Hashimoto thyroiditis

Definition

• Autoimmune destruction of the thyroid gland
• Characterized clinically by gradual thyroid failure, with or without goite formation
• The major cause of Hypothyroidism in adults
  • Enlarged painless thyroiditis

Risk factors

• Genetics
• Autoimmune conditions
• Iodine excess
• Radiation
• Female (4-10:1)

Pathophysiology

• Autoimmune-mediated destruction of thyrocytes
• Formation of immune complexes and compliment in basement membrane of follicular cells
• Thyroid function altered
  • Impaired T3 and T4 production due to TPO inhibition
  • Infiltration of lymphocytes and resultant fibrosis
  • “Chronic lymphocytic thyroiditis”
  • Decreased number and efficiency of thyroid follicles
• Autoantibodies
  • Presence of Thyroid Peroxidase antibodies (anti –TPO Abs) can be detected
  • Many also have antibodies that block TSH

Management

• Thyroid hormone replacement

Acute Suppurative Thyroiditis

• Extremely rare
• Usually result of severe pyogenic infection of upper airway
  • Can be related to piriform sinus fistula or other congenital abnormalities
• Results in severe localised pain
  • Usually unilateral
• Staph aureus and Streptococcus most common organisms
• Treatment is to drain abscess and give antibiotics
• Long-term effects on thyroid rare

Subacute Thyroiditis

• De Quervain’s Thyroiditis

Clinical features

Characterised by

• Neck pain
• A tender diffuse goiter
• A predictable course of thyroid function evolution
  • Hyperthyroidism is typically the presentation, followed by euthyroidism, hypothyroidism, and ultimately restoration of normal thyroid function

Cause

• Presumed to be caused by a viral infection or a postviral inflammatory process
  • Usually have preceding hx of URTI (? Coxsackie)
  • Destructive thyroiditis causes release of pre-formed hormones

Risk factors

• Predominates in women (2:1), mean age 40
• Mostly in US, England and Japan

Symptoms

• Diffuse cervical swelling and pain
• 2/3 patients have fever, weight loss and severe fatigue
• Usually hyper, then hypothyroidism, then resolution and normal function

Diagnosis

• Usually clinically
• FNA can be diagnostic
  • Giant Cells of epithelioid foreign body type (characterises lesion)
• Microscopy shows
  • Large follicles infiltrated by mononuclear cells, neutrophils, and lymphocytes
• RAI uptake decreased

Treatment

• Don’t affect disease process
• Usually self-limiting (90-95% in months)
• Pain
  • Steroids or NSAIDs relieve symptoms
• Hyerthyroid
  • Short lived
  • Supportive Rx (β-B for tachycardia)
• Hypothyroid
  • Often nothing needed
  • If needed then for 6-8 weeks and then discontinued and patient reevaluated

Riedel Thyroiditis

• Invasive fibrous thyroiditis
  • Etiology is not known
    • Often believed to be the local involvement of the thyroid in a systemic disease and may occur with other fibrosing conditions such as retroperitoneal fibrosis, fibrosing mediastinitis, sclerosing cholangitis, pancreatitis etc
    • May occur within the spectrum of immunoglobulin G4 (IgG4)-related systemic disease
• Extremely rare
• Characterised by firm thyroid
  • Associated with a mononuclear cell inflammation that extends beyond the thyroid into the perithyroidal soft tissue
• Symptoms
  • Severe discomfort from extension into Trachea, Oesophagus, RLN
  • Can make surgery difficult with planes obliterated
  • May have impending airway obstruction or dysphagia
• Pathology:
  • Dense fibrous tissue and almost total obliteration of normal follicles
• Management
  • Thyroid hormone replacement, Steroids or Tamoxifen may be effective
  • Surgery if tracheal/oesophageal obstruction imminent
  • Needs to be experienced surgeon