Thyroid function in the intensive care unit setting

The purpose of this article is to summarize the alterations in thyroid func tion that occur in the intensive care unit setting and to discuss in detail several specific conditions (e.g., medications, fasting, infections, malig nancy AIDS). The majority of patients in the intensive care unit who have t hyroid function test changes are thought to be euthyroid. These individuals typically have a normal or decreased free T4, decreased total T3 and norma l thyorid stimulating hormone (TSH), a constellation of homeostatic finding s that are referred to as "the euthyroid sick syndrome." However, there are patients in the intensive care unit who actually have biochemically pertur bed thyroid function with altered thyroid hormone levels in peripheral tiss ues, resulting in either hypothyroidism or hyperthyroidism. It is usually d ifficult to discern these patients from the larger population of euthyroid patients, partly because the usual clinical manifestations of hyperthyroidi sm or hypothyroidism overlap with the signs and symptoms of euthyroid patie nts who have altered thyroid function tests. This article will describe imp ortant aspects of these conditions.