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Thyroid function in nonthyroidal illness

Douglas S Ross, MD
Section Editor
David S Cooper, MD
Deputy Editor
Jean E Mulder, MD


Assessment of thyroid function in patients with nonthyroidal illness is difficult, especially among those hospitalized in an intensive care unit (ICU). Many of them have low serum concentrations of both thyroxine (T4) and triiodothyronine (T3), and their serum thyroid-stimulating hormone (TSH) concentration also may be low. Previously, these patients were thought to be euthyroid, and the term euthyroid-sick syndrome was used to describe the laboratory abnormalities [1]. However, there is evidence that these patients may have acquired transient central hypothyroidism [1].

Despite these abnormalities, treatment of these patients with thyroid hormone, while controversial, appears to be of little benefit and may be harmful [2]. It is possible that the changes in thyroid function during severe illness are protective in that they prevent excessive tissue catabolism [2].

This topic will review the changes in thyroid hormone and TSH metabolism that can occur in patients with nonthyroidal illness. The utility of the different tests to assess thyroid function is discussed separately. (See "Laboratory assessment of thyroid function".)

There are two important general principles [3]:

Thyroid function should not be assessed in seriously ill patients unless there is a strong suspicion of thyroid dysfunction.

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Literature review current through: Nov 2017. | This topic last updated: Jun 21, 2017.
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