Endocrine: Thyroiditis & Hypothyroidism

Thyroiditis & Hypothyroidism

Thyroiditis

  • Definition: Thyroid Inflammation
  • May Initially Present as Transient Thyrotoxicosis/Hyperthyroidism Although It Will Eventually Cause a Hypothyroid State

Presentation

  • Symptoms of Hypothyroidism:
    • Fatigue
    • Weight Gain
    • Depression
    • Cold Intolerance
    • Constipation
  • Symptoms of Mass Effect:
    • Neck Pain
    • Dysphagia
    • Dyspnea
    • Hoarseness
    • Goiter

Causes

  • Painless Thyroiditis
    • Hashimoto’s Thyroiditis
    • Postpartum Thyroiditis
    • Riedel’s (Fibrous) Thyroiditis
    • Drug-Induced Thyroiditis
  • Painful Thyroiditis
    • De Quervain/Subacute Thyroiditis
    • Acute Suppurative Thyroiditis
    • Trauma-Induced Thyroiditis
    • Radioiodine-Induced Thyroiditis
  • Non-Thyroiditis Causes:
    • Euthyroid Sick Syndrome – Low T3 from Decreased Peripheral Conversion in Critically Ill Patient
    • Total or Partial Thyroidectomy
    • Cervical Radiation Therapy
    • Iodine Deficiency
    • Decreased TSH Secretion by the Pituitary Gland

Disorders & Diagnosis

Hashimoto’s (Chronic Autoimmune) Thyroiditis

  • Most Common Cause of Hypothyroidism
  • Pathophysiology: Autoimmune-Mediated Destruction of the Thyroid
    • Antibodies: Anti-Thyroglobulin (TG), Anti-Thyroid Peroxidase (TPO) & Anti-Microsomal
    • Associated with Increased Iodine Intake
  • More Common in Women (7:1) Between Ages 30-50
  • Most are Asymptomatic & Painless
  • Increased Risk for Thyroid Lymphoma
  • Diagnosis: US & Antibody Measurement
    • US: Heterogenous & Diffusely Enlarged
    • FNA if Rapidly Enlarging (Rule Out Lymphoma)
      • Biopsy: Lymphocytic Infiltrate with Germinal Centers, Hürthle Cells, Fibrosis & Small Follicles with Decreased Colloid

Postpartum Thyroiditis

  • Generally Considered a Variant of Hashimoto’s Thyroiditis
  • Pathophysiology: Autoimmune-Mediated Destruction of the Thyroid within 1-Year of Pregnancy
    • Associated with Similar Antibodies to Hashimoto’s Thyroiditis
  • Most are Asymptomatic & Painless
  • Prognosis:
    • Most are Self-Limited & Resolve After 6-12 Months with No Residual Dysfunction
    • Recurrence is Common
    • 4-46% Develop Permanent Hypothyroidism within 3-12 Years
      • Strongest Risk Factor for Permanent Dysfunction: Higher TPO-Ab Titers & TSH > 20 mU/L
  • Diagnosis: US & Antibody Measurement
    • Biopsy: Lymphocytic Infiltrate without Germinal Centers, Hürthle Cells or Fibrosis

Riedel’s (Invasive Fibrous) Thyroiditis

  • Fibrotic Replacement of Thyroid Tissue
    • Fibrosis Can Extend Beyond the Capsule into Peri-Thyroid Tissue (May Affect Parathyroids & Cause Hypoparathyroidism)
    • No Relationship to Autoimmune Disease or Drugs
  • Fibrosis May Also Involve Other Extra-Thyroidal Sites (Retroperitoneum, Mediastinum, Lungs & Parotid Glands)
  • Thyroid Gland is Nontender & “Stone-Hard”/“Hard as Wood”
  • Diagnosis: Thyroid Function Tests, US & CT/MRI
    • US: Hypoechogenic, Reduced Vascularity & Difficult Demarcation of Thyroid from Surrounding Structures
    • Biopsy: Extensive Fibrotic Change with a Paucity of Follicular Epithelium

Drug-Induced Thyroiditis

  • Potential Causes:
    • Amiodarone
    • Interferon-α
    • Interleukin-2 (IL-2)
    • Tyrosine-Kinase Inhibitors (Sunitinib/Imatinib)
    • Lithium
  • Most are Painless
  • 10% Will Develop Hashimoto’s Thyroiditis or Graves’ Disease
    • Strongest Risk Factor: Increased Anti-Thyroid Ab Prior to Causative-Drug Initiation
  • Amiodarone-Induced Thyrotoxicosis (AIT)
    • Can Potentially Cause Both Hypothyroidism & Hyperthyroidism (From High Iodine Content)
    • Highly Lipophilic with 100 Day Half-Life
      • Can Cause Toxicity Well After Drug Discontinuation
      • No Immediate Benefit to Drug Discontinuation in Treatment
    • Type I: Iodine-Induced Increase in Thyroid Hormone Synthesis
      • More Common in Preexisting Thyroid Disease
      • US Shows Increased Vascularity
    • Type II: Direct Toxicity Causes Destructive Thyroiditis
      • More Common in Those Without Preexisting Thyroid Disease
      • US Shows Absent Vascularity

Subacute (De Quervain) Thyroiditis

  • Also Known As: Subacute Granulomatous Thyroiditis or Subacute Nonsuppurative Thyroiditis
  • Thyroid Inflammation Preceded by Viral Infection
  • More Common in Women Aged 30-40
  • Causes Severe Pain Mn
    • May Be Unable to Tolerate Tight-Fitting Clothes or Physical Palpation
  • Most are Self-Limited & Resolve After 1-3 Months with No Residual Dysfunction
    • Risk for Permeant Hypothyroidism: 15%
  • Diagnosis: Clinical
    • Labs: Leukocytosis with Elevated ESR/CRP
    • US: Heterogenous & Hypoechoic with Decreased Vascularity

Acute Suppurative Thyroiditis

  • Abscess from Bacterial Infection
  • Most Common Organisms: Staphylococcus & Streptococcus
    • Most Arise from Hematogenous Spread
  • Most Common in Immunocompromised
    • Thyroid is Normally Highly-Resistant to Infection Due to High-Vascularity with Extensive Lymphatic Drainage
  • Diagnosis: US & FNA/Culture

Trauma-Induced Thyroiditis

  • Causes:
    • Trauma
    • Neck Surgery or Biopsy
    • Vigorous Physical Exam
  • Generally Self-Limited without Any Intervention

Radioiodine-Induced Thyroiditis

  • Presents with Mild Neck Pain 5-10 Days After Treatment
  • Generally Resolves in 5-10 Days

Treatment

Primary Treatment

  • Primary Hypothyroid Management: Thyroid Hormone Replacement
  • Pain Relief from Thyroiditis: NSAID’s (First Line)
    • If Fails After 2-3 Days: Steroids
  • Surgery Indications:
    • Compressive Symptoms
    • Concern for Malignancy
    • Cosmesis

Thyroid Hormone Replacement

  • Preferred Replacement: Synthetic Thyroxine (T4)
    • Levothyroxine (Synthroid)
  • Goal: Normal TSH Levels & Symptom Relief
  • For Elderly or Coronary Artery Disease: Reduce Initial Dose to Prevent Overtreatment
  • Triiodothyronine (T3) is Rarely Indicated for Very Select Patients

Management of Specific Etiologies

  • Riedel’s Thyroiditis:
    • Primary Treatment: Steroids
    • Airway Obstruction: Isthmusectomy (More Extensive Surgery is High-Risk for Injury to Surrounding Structures Due to Loss of Normal Tissue Planes)
  • Amiodarone-Induced Thyrotoxicosis (AIT):
    • Type I: Thioamides (Methimazole) or Radioactive Iodine (RAI)
    • Type II: Steroids
    • If Either Fail: Total Thyroidectomy
  • Acute Suppurative Thyroiditis:
    • Primary Treatment: Antibiotics & Percutaneous Drainage
    • If Fails: Surgical Drainage

Mnemonics

Presentation of Subacute (De Quervain) Thyroiditis

  • DeQuer-“Vain” Causes Severe “Pain”