title: [Evaluation of serum levels of thyroid hormones in myocardial revascularization.].
abstract: OBJECTIVE
  Thyroid hormones, thyroxine (T4) and triiodothyronine (T3), regulate anabolism of proteins, lipids, and carbohydrates, and increase oxygen consumption. Surgical stress and cardiopulmonary bypass (CPB) can change active hormone levels by interfering with the peripheral conversion and reducing serum levels of T3, without changing the levels of thyrotropin (TSH), which are the characteristics of the euthyroid syndrome. The objective of this work was to compare serum levels of T3, T4 and TSH in patients undergoing myocardial revascularization (MR) with or without ECC.
  
  
  METHODS
  Eighteen patients scheduled for elective MR divided as follows: CPB Group (n = 9): patients undergoing CPB, and the Group without CPB (n = 9): patients that did not undergo CPB. The serum levels of T3, T4 and TSH were determined before anesthetic induction (initial OR), at the end of the surgery (final OR), in the first (1st PO) and in the second (2nd PO) postoperative days. Statistical analysis (Analysis of Variance for repeated measures, Mann-Whitney test, and Friedman test) considered significant a p < 0.05.
  
  
  RESULTS
  There was a reduction in serum levels of T3 in both groups. Serum levels of T4 showed differences in final OR and 1st PO, which were elevated in the group that did not undergo CPB. Serum levels of TSH remained within normal limits.
  
  
  CONCLUSIONS
  Serum levels of T3 are reduced after myocardial revascularization with and without CPB, with greater reduction in T4 in the group that underwent CPB. The absence of pituitary response to changes in serum levels of T3 and T4 characterized the euthyroid syndrome in both groups.
authors.affiliation: Instituto do Coração, Hospital das Clínicas, Faculdade de Medicina, Universidade de São Paulo.
authors.forename: Elaine Rahal Rodas
authors.initials: ER
authors.lastname: Messias
authors.forename: José Otávio Costa
authors.initials: JO
authors.lastname: Auler
authors.forename: Maria José Carvalho
authors.initials: MJ
authors.lastname: Carmona