Thyroid, Euthyroid Sick Syndrome

The euthyroid sick syndrome, also known as nonthyroidal illness syndrome, refers to changes seen in patient thyroid function tests administered in the medical intensive care unit during episodes of critical illness. It is not a true syndrome, and there are significant alterations in the hypothalamic-pituitary-thyroid axis in about 75% of the hospitalized patients. This condition often is seen in patients with severe critical illness, deprivation of calories, and following major surgeries. The most common hormone pattern in sick euthyroid syndrome is a low total T3 and free T3 levels with normal T4 and thyroid-stimulating hormone levels.[1][2][3]