الفهرس 
INTRODUCTIONOnly 14 pages are availabe for public view
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Abstract
The non-thyroidal illness syndrome, also known as the low T3 syndrome or euthyroid sick syndrome, describes a condition characterized by abnormal thyroid function tests encountered in patients with acute or chronic systemic illnesses. The laboratory parameters of this syndrome include low serum levels of triiodothyronine (T3) and high levels of reverse T3, with normal or low levels of thyroxine (T4) and normal or low levels of thyroid-stimulating hormone (TSH). This condition may affect 60% to 70% of critically ill patients. The changes in serum thyroid hormone levels in the critically ill patient seem to result from alterations in the peripheral metabolism of the Thyroid hormones, in TSH regulation, in the binding of thyroid hormone to transport-protein and in receptor binding and intracellular uptake. Medications also have a very important role in these alterations. Hormonal changes can be seen within the first hours of critical illness and, interestingly; these changes correlate with final outcome. Data on the beneficial effect of thyroid hormone treatment on, outcome in critically ill patients are so far controversial.
Hypothyroidism is difficult to diagnose clinically, especially in the elderly. Although it is a fairly uncommon cause of ventilator-dependent respiratory failure, with an incidence of 3%, it is a potentially treatable condition. All patients with difficult weaning from ventilatory support should be routinely evaluated and screened for thyroid functions. The role of fT3 concentration as a potential prognostic marker in respiratory patients is not surprising in view of its importance in maintaining the homeostasis of almost all organ systems, and its role in modulating systemic adaptations to acute injury. In this regard, fT3 could be more useful than systemic (APACHE II score) and organ specific (PaO2/FiO2 ratio) functional parameters as an additional predictor of outcome.