• Any enlargement of the thyroid gland
  • Classification on the basis of
    • Location (cervical vs. substernal)
    • Morphology (diffuse vs. nodular)
    • Functional status (hypothyroid, euthyroid, or hyperthyroid)
    • Etiology (autoimmune, neoplastic, etc.)


Varies according to dietary iodine

  • 5–7% in areas with iodine-replete diet
  • >20% in iodine-deficient areas

Etiology and Pathophysiology

  • Iodine deficiency is major cause worldwide.
  • Iodine excess
    • Japanese diets high in seaweed and fish
  • Certain drugs and foodstuffs
    • Lithium
    • Vegetables with thiocyanate metabolite
  • Heavy smoking (multinodular goiter)
  • Infiltration of gland
    • Inflammatory cells (thyroiditis)
    • Tumor cells (lymphoma, thyroid cancer)
  • TSH receptor activation
    • Autoimmune thyroiditis
    • Drugs
    • Pituitary adenoma
    • Thyroid hormone resistance
  • Genetics
  • Idiopathic


  • Uncertain but suspected role in some cases
  • Familial predisposition
  • Occasional gene mutations affecting hormone synthesis

Risk Factors

  • Dietary iodine (deficient or excessive)
  • Heavy smoking
  • Family history
  • Female:male = 4:1

General Prevention

Adequate iodine intake

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