IL-6 and thyroid hormones in critically ill patients with sepsis

ABSTRACT

The aim of this study was to investigate whether the activation of the cytokine system, in particular, activation of interleukin-6 production, has a role in pathogenesis of thyroid hormones changes in critically ill patients with sepsis. Thirty one patients with sepsis were studied at the Critical Care Medicine department at Alexandria Main University Hospital. Clinical evaluation of the severity of illness was done using sepsis related organ failure score [SOFA score]. Blood samples were obtained within 6 hours after admission and were collected with EDTA. Plasma was separated by centrifugation at 3000rPM for 10 minutes and stored at -80°C until assayed. 10 blood samples were obtained from healthy volunteers [5 males and 5 females] as control group. These plasma samples were used for measurement of inerleukin-6 [IL-6], free thyroxine [fT4], free triiodothyronine [f T[3]] and thyroid stimulating hormone [TSH]. Serum interleukin-6 level was significantly higher in patients with sepsis than control group [mean +/- SD was 100.904 +/- 10.941 pg/ml versus 26.652 +/- 5.125 pg/ml respectively, P = 0.0001*]. The patients were divided into 4 groups according to SOFA score. It was found that fT3 and FT4 levels were significantly decreased with increased severity of sepsis [F= 20.306, P=.000* and F= 7.025, P= .001* respectively], while serum levels of IL-6 were increased significantly with the increased severity of sepsis [F =18.55, p =.000*]. A significantly positive correlation was found between IL-6 and SOFA score, [r = .823, P .000*] while significantly negative correlation was found between levels of fT3 and serum IL-6 levels and SOFA score, [r= -.887, P = .000* and r = -.866, P= .000* respectively]. Also, a significant negative correlation was found between levels of fT4 and serum IL-6 levels and SOFA score [r= -.597. P =.000* and r= -.579, P = .000* respectively]. Also, there was a negative correlation between TSH, IL-6 and SOFA score levels but significant only with IL-6 levels [r= -0.407, P= .023* and r= -.0085, P= 0.649 respectively.] This study demonstrated that there is a positive correlation between serum level of IL-6 and severity of sepsis as it was significantly increased with increased SOFA score. While fT3, fT4 and TSH levels are significantly decreased with increased levels of IL-6. So, these suggest that the activation of the cytokine system, in particular, activation of interleukin-6 production, has a role in pathogenesis of thyroid hormones changes in critically ill patients with sepsis