Last revised by Dr Daniel J Bell on 14 Jun 2021

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

Hyperthyroidism is not synonymous with thyrotoxicosis, the latter referring to a clinical syndrome of excess thyroid hormone 1

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 a subclinical form of hyperthyroidism (i.e. lacking thyrotoxicosis), but this is less common 1.

Thyrotoxicosis predisposes patients to a variety of tachydysrhythmias, as well as atrial and ventricular ectopy 2:

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

Numerous causes of hyperthyroidism exist 1:

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