• Decreased level of thyroid hormone leads to a variety of clinical manifestations
  • More common in women and the elderly
  • Myxedema coma is a rare, extreme form of hypothyroidism characterized by altered mental status and defective thermoregulation triggered by a precipitating event in a patient with hypothyroidism


  • Primary:
    • Idiopathic
    • Congenital
    • Autoimmune:
  • Thyroiditis
  • Hashimoto disease
    • Iatrogenic:
  • Postsurgical
  • External radiation
  • Radioiodine therapy
  • Drugs:
  • Iodides, lithium, amiodarone, sunitinib, bexarotene, interferons, narcotics, sedatives
  • Phenytoin and carbamazepine increase clearance of T4 in patients with hypothyroidism taking T4
    • Neoplasm: Primary (carcinoma) or secondary (infiltration)
    • Infection: Viral (rarely aerobic or anaerobic bacteria)
    • Iodine deficiency (most common cause worldwide)
  • Central (very rare):
    • Pituitary or hypothalamic disorder induced by drugs or severe illness
    • May have other associated hormone deficiencies
  • Myxedema coma:
    • Life-threatening decompensation of a patient with hypothyroidism due to a stress, often during winter months
    • Stressors include:
  • Infection
  • Hypothermia
  • Intoxication
  • Drugs (e.g., opioids)
  • Cerebrovascular accident
  • Heart failure
  • Trauma

Pregnancy Considerations
  • Hypothyroidism has been associated with preterm delivery, placental abruption, preeclampsia, low birth weight, and increased rate of Caesarean section
  • Hypothyroid women require increased exogenous thyroid hormone replacement during pregnancy above baseline
  • Postpartum thyroiditis occurs in up to 10% of women:
    • Usually 3–6 mo postpartum
    • Typically resolves without treatment

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