![]() ![]() After discharge from the hospital, thyroid function abnormalities may persist for several weeks. ![]() Treatment and management of underlying medical illness is the main focus however, periodic monitoring of thyroid function should be done while the patient is in the hospital. Thyroid hormone replacement is generally not needed in patients with euthyroid sick syndrome. No imaging studies or thyroid biopsy are necessary or play any role in evaluating and managing the euthyroid sick syndrome. HIV patients have unusual variations of thyroid function, causing an increase in the T4 and TBG levels, decreases in the reverse T3 and rT3/T4 ratio, and normal T3 and T3/T4 ratio. These substances cause a decrease in the hepatic uptake of T4 and 5' monodeiodination of T4 to T3, and they can potentially precipitate hyperthyroidism in patients with an autonomous thyroid nodule by accelerating the Jod Basedow phenomenon. Total, as well as free T4 concentrations, are increased in patients who have been treated or exposed to amiodarone and radiocontrast agents such as iopanoic acid. Serum thyroid binding globulin level is increased in patients with acute intermittent porphyria and chronic hepatitis, causing normal free T4 and high serum total T4 levels. ![]() ![]() The free T4 level is reduced in euthyroid sick syndrome patients who had received treatment with drugs like dopamine and steroids that promote decreased TSH levels. This combination of findings in euthyroid sick syndrome has been explained by the presence in the circulation of a thyroid-binding hormone inhibitor. Low serum total T4 correlates with a bad prognosis thyroid binding globulin level is usually within normal, and the free T4 index is low in those patients. Elevated rT3 level is predominantly due to decreased activity of the type I iodothyronine 5'-monodeiodinase (deiodination of T4 to T3 as well as rT3 to 3,3'-diiodothyronine).īoth low T3 and low T4 syndrome are usually observed in the most critically ill patients admitted to intensive care units. The serum level of reverse T3 (rT3) is increased in euthyroid sick syndrome, except in renal failure. Low serum total T3 level is the most common abnormality in euthyroid sick syndrome, and it is seen in about 70% of hospitalized patients. Aspirin and heparin drugs impair the protein binding of the thyroid hormones, causing the reduction of total T3 and T4 levels and, subsequently, temporary elevation of free T3 and T4 levels.Įuthyroid sick syndrome has been classified as (1) low T4 syndrome, (2) low T3 and low T4 syndrome, (3) high T4 syndrome, and (4) other abnormalities of the thyroid. The fall in serum albumin level in euthyroid sick syndrome enhances the activity of different competitors of T4 on thyroid-binding globulin. Serum albumin binds to fatty acids, which displaces thyroid hormones from the thyroid-binding globulin. Several other mechanisms can contribute to the inhibition of 5'-monodeiodination, causing a decrease in the concentration of serum total T3 levels in patients with a nonthyroidal illness, such as high serum cortisol and the use of exogenous corticosteroid therapy, as well as other medications like amiodarone and propranolol. The peripheral deiodinase activity type 1 is downregulated, and the central type 2 and type 3 deiodinase activities are up-regulated in critically ill patients. Cytokines were also thought to reduce the activity of type 1 deiodinase and decrease the binding capacity of the T3 nuclear receptors. The euthyroid sick syndrome is also caused by cytokines such as interleukin 1, interleukin 6, tumor necrosis factor-alpha, and interferon-beta affecting the hypothalamus and pituitary glands, thus inhibiting TSH, thyroid-releasing hormone (TRH), thyroglobulin (TG), T3, and the thyroid-binding globulins (TBG) production. One cause suggested is when the presence of thyroid-binding hormone inhibitors in the serum and different body tissues inhibits the binding of the thyroid hormone to the thyroid-binding protein. There are many proposed mechanisms regarding the pathogenesis of euthyroid sick syndrome. ![]()
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