hyperthyroidism

Hyperthyroidism refers to increased production and secretion of thyroid hormone from the thyroid gland.

Terminology

Hyperthyroidism is not synonymous with thyrotoxicosis, the latter referring to a clinical syndrome of excess thyroid hormone.

Clinical presentation

Hyperthyroidism may be accompanied by the signs and symptoms of thyrotoxicosis (e.g. heat intolerance, weight loss, tremor). However, it is also possible to have subclinical hyperthyroidism (i.e. lacking thyrotoxicosis), but this is less common .

ECG
  • sinus tachycardia
  • high voltage QRS complexes
  • atrial fibrillation

Thyrotoxicosis predisposes patients to a variety of tachydysrhythmias, as well as atrial and ventricular ectopy :

  • paroxysmal supraventricular tachycardia (PSVT)
  • non-specific ST segment and T wave changes
    • elderly patients may have rate-related ischemia
  • premature ventricular complexes (PVCs)

Pathology

Etiology

Numerous causes of hyperthyroidism exist :