Myxedema coma is a state of decompensated hypothyroidism. A person may have lab values identical to a "normal" hypothyroid state, but a stressful event (such as an infection, myocardial infarction or stroke) precipitates the myxedema coma state, usually in the elderly. Primary symptoms of myxedema coma are altered mental status and low body temperature. Low blood sugar, low blood pressure, hyponatremia, hypercapnia, hypoxia, slowed heart rate, and hypoventilation may also occur. Myxedema, although included in the name, is not necessarily seen in myxedema coma.
According to newer theories myxedema coma could result from allostatic overload in a situation where the effects of hypothyroidism are amplified by non-thyroidal illness syndrome.