Description

• 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.)

Epidemiology

Prevalence
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

Genetics

• 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