Sick euthyroid syndrome (SES), is the most common endocrine disorder in critically ill patients.(5) This syndrome is defined as low levels of tri- iodothyronine (T3), low or normal levels of thyroxine (T4) and normal levels of thyroid stimulating hormones (TSH) in the serum.(6). In critically ill patients, the most common disorder in thyroid hormones is low T3 levels.(7) Additionally, T4 level also decreases with disease severity(8-10) and it has been shown that low T4 level is associated with prognosis.(10-13)