Thyroid function in the intensive care unit setting

The purpose of this article is to summarize the alterations in thyroid function that occur in the intensive care unit setting and to discuss in detail several specific conditions (e.g., medications, fasting, infections, malignancy AIDS). The majority of patients in the intensive care unit who have thyroid function test changes are thought to be euthyroid. These individuals typically have a normal or decreased free T4, decreased total T3 and normal thyorid stimulating hormone (TSH), a constellation of homeostatic findings that are referred to as the euthyroid sick syndrome. However, there are patients in the intensive care unit who actually have biochemically perturbed thyroid function with altered thyroid hormone levels in peripheral tissues, resulting in either hypothyroidism or hyperthyroidism. It is usually difficult to discern these patients from the larger population of euthyroid patients, partly because the usual clinical manifestations of hyperthyroidism or hypothyroidism overlap with the signs and symptoms of euthyroid patients who have altered thyroid function tests. This article will describe important aspects of these conditions.