A number of serious illnesses mimic and coexist with thyroid storm. The differential diagnosis is broad and includes delirium of any etiology. Sympathomimetic and anticholinergic toxidromes and withdrawal syndromes (ethanol, narcotics, and sedative-hypnotics) resemble thyroid storm. Hypoglycemiainitially presents with a hyperadrenergic state and agitation, like thyroid storm. Hypoxia of any etiology can cause a hyperadrenergic state and altered mental status. Any infection that progresses to sepsis can cause fever, tachycardia, and mental status changes. Central nervous system infections causing encephalitis or meningitis closely resemble thyroid storm. Heat stroke may accompany tachycardia, altered mental status, and, less commonly, hypertension. Drug-induced hypertensive crises usually lack the tachycardia that is present in thyroid storm. It is crucial to recognize that any of these entities may exist concurrently with thyroid storm. Indeed, any of these disease processes may incite thyroid storm. Table 1 lists the key diagnoses in the differential diagnosis of thyroid storm.
With a clinical picture as varied as hypotension, hypothermia, coma, and altered mental status, a similarly broad differential exists for myxedema coma. (See Table 2.) In addition, a broader endocrine disorder such as panhypopituitarism or adrenal insufficiency may be present. Sepsis with hypotension, altered mental status, and hypothermia can closely mimic myxedema coma. Acute heart failure with peripheral edema, cardiomegaly, pleural effusions, and hypotension can be confused with myxedema coma. Ingestions of sedative-hypnotics, narcotics, anesthetics, and heavy metals such as lithium can produce coma. Gastrointestinal bleeding and metabolic disorders must always be in the differential diagnosis.
As with thyroid storm, concomitant illness occurs commonly with myxedema coma and may be
the cause of a patient's deterioration into severe life-threatening hypothyroidism. Common precipitants of myxedema coma include cold exposure, trauma that prevents access to medication, and infections, usually genitourinary or pulmonary. Consider disorders of the thyroid in all patients with systemic illness who have a history of thyroid disease or who are older than 60 years.