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Myxedema coma, the extreme manifestation of hypothyroidism, is an uncommon but potentially lethal condition. Patients with hypothyroidism may exhibit a number of physiologic alterations to compensate for the lack of thyroid hormone. If these homeostatic mechanisms are overwhelmed by factors such as infection, the patient may decompensate into myxedema coma. Patients with hypothyroidism typically have a history of fatigue, weight gain, constipation and cold intolerance. Physicians should include hypothyroidism in the differential diagnosis of every patient with hyponatremia. Patients with suspected myxedema coma should be admitted to an intensive care unit for vigorous pulmonary and cardiovascular support. Most authorities recommend treatment with intravenous levothyroxine (T^sub 4^), as opposed to intravenous liothyronine (T^sub 3^). Hydrocortisone should be administered until coexisting adrenal insufficiency is ruled out. Family physicians are in an important position to prevent myxedema coma by maintaining a high level of suspicion for hypothyroidism. (Am Fam Physician 2000;62:2485-90.)
Myxedema coma is an extreme complication of hypothyroidism in which patients exhibit multiple organ abnormalities and progressive mental deterioration. The term myxedema is often used interchangeably with hypothyroidism and myxedema coma. Myxedema also refers to the swelling of the skin and soft tissue that occurs in patients who are hypothyroid. Myxedema coma occurs when the body's compensatory responses to hypothyroidism are overwhelmed by a precipitating factor such as infection.
A common misconception is that a patient must be comatose to be diagnosed with myxedema coma. However, myxedema coma is a misnomer because most patients exhibit neither the nonpitting edema known as myxedema nor coma.1,2 Instead, the cardinal manifestation of myxedema coma is a deterioration of the patient's mental status.
When only comatose patients are considered, myxedema coma is exceedingly rare: one study reports 200 cases between 1953 and 1996.3 Applying a broader definition results in a significantly higher number of cases. While the actual prevalence of myxedema coma is unknown, its lethal nature demands recognition. Even with early detection and appropriate treatment, mortality ranges from 30 to 60 percent. 3,4 Family physicians must be alert to the possibility of undiagnosed hypothyroidism in their patients.
Epidemiology
Hypothyroidism is four times more common in women than in men; 80 percent of cases of myxedema coma occur in females.5,6 Myxedema coma occurs almost exclusively in persons 60 years...