Hashimoto Thyroiditis

Introduction

• A condition characterized by the autoimmune destruction of the thyroid
• Pathophysiology 
  • the inflammatory reaction is a combination type II and type IV hypersensitivity reaction
    • type II hypersensitivity reaction
      • anti-TSH receptor antibodies are formed that inhibit thyroid hormone release
        • opposite of Grave’s disease
      • anti-microsomal and anti-thyroglobulin antibodies are formed that lead to destruction of thyroid stroma 
        • do not confuse with anti-mitochondrial in primary biliary sclerosis
    • type IV hypersensitivity reaction
      • CD8 cells directly destroy thyroid tissue
      • CD4-attracted macrophages destroy thyroid tissue
• Genetics
  • association with HLA-DR3, DR5 genotype
• Associated conditions
• chromosomal aneuploidies

Presentation

• Symptoms
  • hyperthyroidism
    • seen early in the disease course
    • consequence of thryoid tissue destruction which releases stored thyroid hormones
  • hypothyroidism 
    • seen later in the disease course
    • after pre-formed thyroid hormone stores are released there is a decreased release as a result of impaired production
• Physical exam
• moderately enlarged, non-tender gland

Evaluation

• Histology 
  • lymphocytic infiltrate
  • germinal follicles
  • Hürthle cells (eosinophilic-staining cells)
• fibrosis

Treatment

•  Pharmacologic
• thyroid hormone supplementation

Complications

• Primary B-cell lymphoma of thyroid
  • increased risk of primary B-cell lymphoma of thyroid