Hypothyroidism

Background

  • 3-10x more common in females
  • Peak incidence age >60
  • Emergent manifestation of severe hypothyroid = myxedema coma

Etiology

  • Primary
    • Autoimmune (Hashimoto)
    • Thyroiditis (subacute, silent, postpartum)
      • Often preceded by hyperthyroid phase
    • Iodine deficiency
    • After ablation (surgical, radioiodine)
    • After external radiation
    • Infiltrative disease (lymphoma, sarcoid, amyloid, TB)
    • Congenital
    • Meds
    • Idiopathic
  • Secondary

Clinical Features

Differential Diagnosis

Symptomatic bradycardia

Evaluation

Work-up

  • TSH
  • Total and Free T4
  • Total and Free T3
  • Thyroid Binding Globulin (TBG)
  • Auto-antibodies (anti-TPO, anti-microsomal, anti-Tg)
  • Thyroid ultrasound
  • ECG - bradycardia, low voltage
  • VBG - hypercapnia from hypoventilation, possibly compensated if chronic

Categorization

Type Cause TSH FT4
Primary Failure of thyroid Elevated Low
Secondary Failure of pituitary Low Low
Tertiary Failure of hypothalamus

Management

Disposition

  • Most hypothyroidism is treated as an outpatient
  • Admit and treat severe hypothyroidism or myxedema coma

See Also

References