Thyroid storm or
thyrotoxic crisis is a rare but severe and potentially life-threatening complication of
hyperthyroidism (overactivity of the
thyroid gland). It is characterized by
a high fever (often above 40°C/104°F),
fast and often
irregular heart beat,
vomiting,
diarrhea and
agitation.
Heart failure may occur, and
myocardial infarction is encountered. Death may occur despite treatment. Most episodes occur either in those with known hyperthyroidism whose treatment has been stopped or become ineffective, or in those with untreated mild hyperthyroidism who have developed an intercurrent illness (such as an infection).