RELATIONS BETWEEN THE SELENIUM STATUS AND THE LOW T3 SYNDROME AFTER MAJOR TRAUMA

Objective:Thyroxine (T-4) is deiodinated to triiodothyronine (T-3) by the hepatic type I iodothyronine deiodinase, a selenoprotein that is s ensitive to selenium (Se) deficiency. After severe injury, T-4 deiodin ation is decreased, leading to the low T-3 syndrome. Injury increases free radical production, which inactivates the iodothyronine deiodinas e. The aims were to study the Se status after major trauma and to inve stigate its relation to the low T-3 syndrome. Design: Preliminary pros pective descriptive study. Setting: Intensive care unit at a universit y teaching hospital. Patients and methods: 11 patients aged 41 +/- 4 y ears (mean +/- SEM), with severe multiple injuries (Injury Severity Sc ore 29+/-2 points). A balance study was performed from day 1 to day 7. Serum and urine samples were collected from the time of admission unt il day 7, then on days 10, 15, 20, 25 and 30. Nonparametric tests and Pearson's correlation coefficients were used for analysis. Results: Cu mulated Se losses were 0.88+/-0.1 mu mol/24 h. Serum Se was decreased from admission to day 7. T-3, free T-3, and the T-3/T-4 ratio were low until day 5, being lowest on day 2; T-4 and thyroid stimulating hormo ne were normal. Serum Se was correlated with T-3 (r = 0.55, p = 0.0001 ), and with free T-3 (r = 0.35). Conclusion: Se status is altered afte r trauma, with decreased Se serum levels upon admission to the ICU but with no major Se losses. Se is probably redistributed to the tissues. The correlation between Se and T-3, along with the parallel decrease in T-4 deiodination, indicates that reduced deiodination might be rela ted to the transient decrease in serum Se.