Abnormalities of thyroid hormone metabolism during systemic illness: the low T3 syndrome in different clinical settings.

• Grant number: 16/19666-7
• Support Opportunities: Regular Research Grants - Publications - Scientific article
• Start date: November 01, 2016
• End date: April 30, 2017
• Field of knowledge: Health Sciences - Medicine - Medical Clinics
• Principal Investigator: Denise Engelbrecht Zantut Wittmann
• Grantee: Denise Engelbrecht Zantut Wittmann
• Host Institution: Faculdade de Ciências Médicas (FCM). Universidade Estadual de Campinas (UNICAMP). Campinas , SP, Brazil

Abstract

Thyroid hormone abnormalities are common in critically ill patients. For some 3 decades, a mild form of these abnormalities has been described in patients with several diseases under outpatient care. These alterations in thyroid hormone economy are a part of the non-thyroidal illness and keep an important relationship with prognosis in most cases. The main feature of this syndrome is a fall in free triiodothyronine (T3) levels with normal thyrotropin (TSH). Free thyroxin (T4) and reverse T3 levels vary according to the disease in question. The importance of recognizing this condition in such patients is evident to physicians practicing in a variety of specialties, especially general medicine, to avoid misdiagnosing the much more common primary thyroid dysfunctions and indicating treatments that are often not beneficial. This review focuses on the most common chronic diseases already known to present alterations in serum thyroid hormone levels. An illustrative clinical vignette is used as an introduction to the theme followed by a short review of the common pathophysiology of the non-thyroidal illness and the particular laboratorial presentation of each condition. The clinical situations addressed in this review are caloric deprivation, chronic HIV infection, cardiac, renal, liver and pulmonary diseases, diabetes mellitus and psychiatric illnesses. Finally, a short summary on the evidence about treatment of the non-thyroidal illness and future research topics to be addressed are discussed. (AU)