Changes in Free and Total Levels of Plasma Cortisol and Thyroxine Following Thermal Injury in Man

Abstract

Changes in endocrine status are known to occur following thermal injury. Therefore, the effect of burn injury on plasma corticosteroid and and thyroid hormones and their respective binding proteins was examined. Thirty-one subjects with 18%-99% TBSA burn were compared to 50 normal controls with respect to plasma levels of total cortisol, free cortisol, total thyroxine (T4), free thyroxine index (FTI), corticosteroidbinding globulin capacity ICBGC), tri-iodothyronine uptake (T3U), and albumin. Compared to controls, plasma concentrations of total and free cortisol in thermally injured patients were elevated at all time points tested. However, there was no significant difference in total or free cortisol values for survivors and nonsurvivors. Both total T4 and the FTI were significantly decreased compared to normal, and nonsurvivors in turn had significantly lower T4 and FTI values than did survivors. In nonsurviving patients, values of T4 and the FTI were about 50% of the mean value for normal controls, and these levels showed only a slight increase by postburn day (PBD) 21. For both survivors and nonsurvivors, CBGC was decreased relative to normals in the 48-hour period following burn, but by PBD 7 survivors and nonsuivivors had mean levels of CBGC within the normal range. Plasma albumin was uniformly decreased throughout, and there was no difference in levels for survivors and nonsurvivors. These data confirm that thermally injured human beings have increased levels of free and total corticosteroids and decreased levels of T4, and that these changes are more extreme in patients with greater illness who eventually die.