Sick euthyroid syndrome. What to do when thyroid function tests are abnormal in critically ill patients.

Abnormal thyroid hormone concentrations are common in patients with serious nonthyroidal illnesses. Early evidence suggests that thyroid hormone levels may predict the prognosis for some patients. Abnormal thyroid function is usually reversible, but thyroid function tests should be repeated when the nonthyroidal illness is resolved. Whether active intervention using thyroid hormone supplements is beneficial or not remains controversial and requires future large-scale investigation.