Non-Thyroidal Illness

Abstract

The non-thyroidal illness syndrome (NTIS) is a term used to describe alterations in thyroid function tests observed in critically ill patients in the absence of intrinsic thyroid disease. Several studies have demonstrated that it has a high prevalence among hospitalized patients and it is significantly associated with the severity and the outcome of the disease. In the last decades there has been a shift in our view of the pathogenetic mechanisms underlying the syndrome. It has been increasingly recognized that alterations in the hypothalamus and the pituitary play a predominant role in the pathogenesis of NTIS, whereas the contribution of peripheral pathways, such as deiodinase activity, does not seem to be as significant as considered in the past. The majority of studies agree that treatment with thyroid hormone (TH) is not beneficial. However, TH may be reserved as an option for high-risk patients with very low TH levels and protracted disease, in whom some degree of hypothyroidism may be present.