Hypothyroidism

Description

• 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

Etiology

• 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

• 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