Tóm tắt

Euthyroid sick syndrome can be described as abnormal findings on thyroid function tests that occur in the setting of a nonthyroidal illness (NTI), without preexisting hypothalamic pituitary and thyroid gland dysfunction. Multiple alterations in serum thyroid function test findings have been recognized in patients with a wide variety of NTIs without evidence of preexisting thyroid or hypothalamic-pituitary disease. The most prominent alterations are low serum triiodothyronine (T3) and elevated reverse T3 (rT3), leading to the general term "low T3 syndrome." Thyroid-stimulating hormone (TSH), thyroxine (T4), free T4 (FT4), and free T4 index (FTI) also are affected in variable degrees based on the severity and duration of the NTI. As the severity of the NTI increases, both serum T3 and T4 levels drop and gradually normalize as the patient recovers. Despite these abnormalities, treatment of these patients with thyroid hormone, while controversial, appears to be of little benefit and may be harmful. It is possible that the changes in thyroid function during severe illness are protective in that they prevent excessive tissue catabolism.