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CRITICAL CARE AND TRAUMA

Free Cortisol in Sepsis and Septic Shock

Stepani Bendel, MD^*, Sari Karlsson, MD, Ville Pettilä, MD, PhD, Pekka Loisa, MD, Marjut Varpula, MD, Esko Ruokonen, MD, PhD^* For the Finnsepsis Study Group

From the Department of Intensive Care, *Kuopio University Hospital, Kuopio, Finland, Tampere University Hospital, Tampere, Finland, Helsinki University Hospital, Helsinki, Finland, and Päijät-Häme Central Hospital, Lahti, Finland.

Address correspondence to Stepani Bendel, MD, Department of Intensive Care, Kuopio University Hospital, PL 16222 Kuopio, Finland. Address e-mail to Stepani.Bendel{at}kuh.fi.

	Abstract

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BACKGROUND: Severe sepsis activates the hypothalamopituitary axis, increasing cortisol production. In some studies, hydrocortisone substitution based on an adrenocorticotropic hormone-stimulation test or baseline cortisol measurement has improved outcome. Because only the free fraction of cortisol is active, measurement of free cortisol may be more important than total cortisol in critically ill patients. We measured total and free cortisol in patients with severe sepsis and related the concentrations to outcome.

METHODS: In a prospective study, severe sepsis was defined according the American College of Chest Physicians/Society of Critical Care Medicine criteria. Blood samples were drawn within 24 h of study entry. Serum cortisol was analyzed by electrochemiluminescence immunoassay. The Coolens method was used for calculating serum free cortisol concentrations.

RESULTS: Blood samples were collected from 125 patients, of whom 62 had severe sepsis and 63 septic shock. Hospital mortality was 21%. Calculated free serum cortisol correlated well with serum total cortisol (r = 0.90, P < 0.001). There was no difference in the total cortisol concentrations in patients with sepsis and septic shock (728 ± 386 nmol/L vs 793 ± 439 nmol/L, P = 0.44). Nonsurvivors had higher calculated serum free (209 ± 151 nmol/L) and total (980 ± 458 nmol/L) cortisol concentrations than survivors (119 ± 111 nmol/L, P = 0.002, and 704 ± 383 nmol/L, P = 0.002). Depending on the definition, the incidence of adrenal insufficiency varied from 8% to 54%.

CONCLUSIONS: Clinically, calculation of free cortisol does not provide essential information for identification of patients who would benefit from corticoid treatment in severe sepsis and septic shock.

	Introduction

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Severe sepsis and septic shock cause numerous endocrinological alterations that may affect a patient’s outcome.1–4 One of the major stress responses is the activation of the hypothalamopituitary–adrenal axis, which increases cortisol production. Cortisol is essential in regulating the impaired vasomotor tone of the vasculature, in affecting the distribution of body fluids, and in sensitizing the catecholamine receptors.5 Adrenal response is frequently disturbed in critically ill patients and small-dose glucocorticoid treatment may reduce morbidity and mortality in selected septic patients with diagnosed adrenal insufficiency.1 Paradoxically, in recent studies, in severe sepsis and septic shock, low total cortisol levels have been associated with favorable outcome, whereas patients with high total cortisol levels have a poor prognosis.6 However, there is continuing debate over how to diagnose possible adrenal insufficiency, and various methods are used for it,2,3,7 including assessment of free unbound serum cortisol.8 The value of the adrenocorticotropic hormone (ACTH) stimulation test has been questioned. Currently, the ACTH stimulation test is no longer included in the Surviving Sepsis Campaign bundles.9 The guidelines suggest that its use be limited to cases in which the diagnosis of adrenal insufficiency is of specific importance.

The controversy over the diagnostic criteria for adrenal insufficiency and ultimately over the role of hydrocortisone treatment has been suggested to be related to confounding factors in sepsis. Normally, up to 90% of cortisol is bound to corticosteroid-binding globulin (CBG). In critical illness, the concentration of CBG decreases markedly. In these conditions, the proportion of biologically active free cortisol increases in a manner which makes the relationship between free and total cortisol unpredictable without CBG/protein measurement. In the current study, which is a substudy of the Finnsepsis study,10 our aim was to assess the relationship between total and calculated free cortisol in severe sepsis and septic shock. In addition, we evaluated the predictive power of calculated serum free and total cortisol with regard to hospital mortality in sepsis and septic shock.

	METHODS

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This was a prospectively defined substudy of the Finnsepsis study, which was a prospective observational cohort study investigating the incidence, associated organ failures, and outcome of severe sepsis in Finland.10 Severe sepsis and septic shock were defined according to the American College of Chest Physicians/Society of Critical Care Medicine criteria.11 Study entry was the time when all criteria for severe sepsis were met. The ethics committee approved the study. Two hundred and fifty patients were enrolled, and 125 were excluded from analysis because of previous corticosteroid treatment (Fig. 1).

View larger version (11K): [in this window] [in a new window]   Figure 1. Flow chart of the study population.

Blood samples were obtained after receiving written informed consent within 24 h of definitive diagnosis of sepsis or septic shock. Samples were stored at –80°C for later analysis. The same personnel did all analyses in one laboratory (Kuopio University Hospital). We used electrochemiluminescence immunoassay (Elecsys Cortisol, Roche Diagnostics, Mannheim, Germany). The Coolens method was used for calculating serum free cortisol concentration12: U² · K (1 + N) + U (1 + N + K (G – T)) – T = 0, where K = affinity of CBG at 37°C, G = CBG, U = unbound cortisol, T = cortisol, and N = the ratio of albumin bound to free cortisol (1.74).

The cut-off values for free cortisol were based on previous studies.7,13,14 A concentration of free cortisol <22 nmol/L and total cortisol <275 nmol/L was considered to be absolute adrenal insufficiency.7 Free cortisol between 22 and 55 nmol/L13,15 and total cortisol concentration between 275 and 500 nmol/L,15 or alternatively between 275 and 690 nmol/L,15 were used to define relative adrenal insufficiency.

Data are presented as mean ± standard deviations (sd) or as absolute values and percentages. Distribution of the parameters was assessed by the Kolmogorov–Smirnov test. For normally distributed parameters, Student’s t-test was used to compare means of different groups. The Mann–Whitney test was used for nonparametric testing between groups. Spearman or Pearson correlations were calculated. Predictive power regarding hospital mortality was assessed by areas under the receiver operating curves (AUC). Outcomes were presented according to the Kaplan–Meier method, and groups were compared with the log-rank method. The analyses were conducted using the SPSS 14.0 software (SPSS, Chicago, IL).

	RESULTS

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Of the 125 study patients, 62 patients had severe sepsis and 63 patients had septic shock. Twenty-seven patients had positive blood culture results. The causes of sepsis were pneumonia (n = 53), intraabdominal infection (n = 35), cellulitis (n = 14), urinary tract infection (n = 7), central nervous system infection (n = 5), endocarditis (n = 5), head/neck infection (n = 2), and unknown (n = 4). The demographic data of the study population are presented in Table 1. In the Finnsepsis study, the hospital mortality was 28.3%.9 The patients (n = 250) included in the laboratory substudy were comparable with all Finnsepsis patients (n = 470) (Fig. 1). However, of those 250, we excluded 125 patients who had received corticosteroid treatment before blood draws. The remaining 125 study patients were not as severely ill. Simplified Acute Physiology Score (SAPS) II points were lower (42 vs 46) for patients who received glucocorticoids than in the rest of the Finnsepsis cohort (P = 0.012), and mortality was also lower for patients who received glucocorticoids (21% vs 31%, P = 0.034). The SAPS II scores were lower in patients who received corticosteroids before blood draws than in those who received corticosteroids after the blood draw (42 vs 46, P = 0.04), but no difference in mortality was detected (21% vs 28%, P = 0.07). After the blood samples were taken, 20 patients received corticosteroids as part of the treatment for septic shock, one patient for treatment of severe sepsis, and 14 patients for other reasons (acute respiratory distress syndrome n = 8, others n = 6). No difference in mortality between those patients who received (n = 35) or who did not receive (n = 90) corticoids (P = 0.18) was detected. There also was no difference in mortality between patients who received corticoids for sepsis and those who did not. Of the patients given corticoids for sepsis, six died. Of those who did not receive corticoids for sepsis, 20 died (P = 0.34). Two patients had received etomidate outside the intensive care unit before blood samples were taken, and both of them survived. Cortisol concentrations in survivors and nonsurvivors are presented in Table 1, in patients with sepsis and septic shock in Table 2, and in patients with or without hydrocortisone treatment in Table 3. The patients received hydrocortisone after the blood samples had been taken. The AUCs are presented for calculated free, total serum cortisol and CBG in Figure 2.

View larger version (8K): [in this window] [in a new window]   Figure 2. Receiver operating characteristic curves regarding hospital mortality for serum total (A) and free (B) cortisol and free/total cortisol (C). Areas under curve (AUC) for serum total cortisol 0.68 (CI: 0.57–0.80), free cortisol 0.70 (95% CI: 0.60–0.81) and for free/total 0.69 (CI: 0.58–0.80).

In general, there was a good correlation between calculated free and total cortisol (Spearman correlation coefficient 0.90, P < 0.001) (Fig. 3). SAPS II and calculated serum free cortisol correlated poorly (Spearman correlation coefficient 0.30, P = 0.001). Absolute adrenal insufficiency in terms of calculated serum free cortisol was detected in 12 patients (7 with severe sepsis and 5 with septic shock), and 2 of them received steroids; all 12 patients survived. Altogether, 25 patients (20%) had relative adrenal insufficiency in terms of calculated serum free cortisol (16 with sepsis and 9 with septic shock), 3 of whom died in the hospital. Four patients with relative adrenal insufficiency in terms of calculated free cortisol concentrations received corticoids, and three of them died. The remaining 88 patients had free cortisol concentrations >55 nmol/L. Their hospital mortality was 26%. Absolute adrenal insufficiency in terms of serum total cortisol was detected in 10 patients, and all survived. Relative adrenal insufficiency in terms of serum total cortisol concentrations (<500 nmol/L) was detected in 27 patients (15 patients with sepsis and 12 patients with septic shock), 3 of whom died. Relative adrenal insufficiency in terms of serum total cortisol concentration of 690 nmol/L was detected in 58 patients (28 with septic shock), 9 of whom (13%) died (P = 0.023 for the increased mortality relative to patients with cortisol concentrations <690 nmol/L). Survival in different categories of cortisol concentration is presented in Figure 4. The figure shows the cumulative survival using cut-off values for serum total cortisol concentrations of 500 nmol/L (Fig. 4A, P = 0.054) or calculated serum free cortisol cut-off values of 55 nmol/L (Fig. 4B, P > 0.1). Patients who received hydrocortisone had higher baseline serum total cortisol concentrations than patients who did not receive hydrocortisone (1030 ± 460 nmol/L vs 707 ± 385 nmol/L, P = 0.002), and had higher calculated free cortisol concentrations (234 ± 145 nmol/L vs 118 ± 112 nmol/L, P = 0.001) and higher free/total serum concentrations (21% ± 7% vs 14% ± 7%, P < 0.001).

View larger version (10K): [in this window] [in a new window]   Figure 3. Baseline total cortisol and free cortisol. Spearman correlation coefficient 0.90, P < 0.001.

View larger version (8K): [in this window] [in a new window]   Figure 4. Kaplan–Meier curves. (A) Serum total cortisol over or <500 nmol/L, P = 0.054, (B) Serum free cortisol over or <55 nmol/L, P > 0.1.

	DISCUSSION

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The main finding of this study was that the relationship between outcome and adrenal function seems to be independent of whether one uses calculated free or total cortisol in the assessment of adrenal function: lower concentrations are associated with a lower calculated free/total cortisol ratio and more favorable outcome. In addition, serum total cortisol concentration correlated well with calculated serum free cortisol. Therefore, calculation of free cortisol concentration, instead of total, most likely does not help to identify patients who could potentially benefit from small-dose glucocorticoid treatment.

In our study, both total and calculated free cortisol concentrations were lower in survivors. This is in agreement with previous studies.2,6,15 Moreover, we demonstrated that the calculated free/total cortisol ratio was lower in survivors. Two studies have evaluated the usefulness of serum-free cortisol measurement,7,13 and the authors suggested measurement of both free and total cortisol. In our study, calculating free cortisol, instead of total cortisol, did not help to distinguish between survivors and nonsurvivors, and gave only moderate discrimination by AUC analysis. Serum total and calculated free cortisol correlated well, and both values were increased in nonsurvivors. Recently, Lipinier-Friedman et al.6 could not demonstrate any difference in total cortisol between patients with severe sepsis and septic shock. Our results agree with this, but in our study, calculated free cortisol levels were significantly higher in the septic shock group. This was most likely due to lower CBG concentrations in patients with septic shock. The survivors of septic shock especially had lower calculated free/total cortisol ratios and lower CBG concentrations than survivors of sepsis without shock. Overall, the hospital mortality was lower than in previous studies with septic shock, as was the case in the entire Finnsepsis cohort. Therefore, the subset of patients in this study was obviously biased because most likely the patients with the most severe septic shock had already received small-dose glucocorticoid treatment, and were excluded. However, this selection does not affect the interpretation of our results, because all the patients had definite severe sepsis and more than half of the patients had septic shock.

The debate regarding the usefulness of total cortisol measurements without an ACTH stimulation test continues.6,16 There are numerous definitions for possible adrenal insufficiency based on a random serum cortisol measurement.3,8,15 In our study, the proportion of patients with adrenal insufficiency varied from 8% to 54% when using different total cortisol cut-off points and from 10% to 30% when using different calculated free cortisol cut-off points. This is in accordance with other studies in which the proportion of patients with adrenal insufficiency varied from 10% to 716 or from 8% to 61%.15 In our study, 30% of the patients had a serum total cortisol level <500 nmol/L or a calculated free cortisol level <55 nmol/L. Although the number of patients in the groups was similar, depending on the criteria used the individual patients, were not the same in these groups. This emphasizes the importance of diagnostic criteria used for adrenal insufficiency. Another confounding factor is the fact that the diagnosis of adrenal insufficiency varies widely depending on the method used for cortisol assays.17

Annane et al. suggested that a threshold of 22 nmol/L for free cortisol be used for identification of adrenal insufficiency.7 To demonstrate the confusion, using serum calculated free cortisol cut-offs <55 nmol/L or serum total cortisol cut-offs of 275 nmol/L would imply that 29% and 8% of the severe sepsis patients, respectively, had adrenal insufficiency. That the severe sepsis patients had good recovery despite the fact that only 2% received corticosteroid treatment raises the question of whether criteria based solely on calculated free or total cortisol can be used for diagnosing clinically relevant adrenal insufficiency. Similarly, our study suggests that neither calculated free nor total cortisol levels should be used as the indication for glucocorticoid treatment; rather, perhaps, the unresponsiveness to fluid therapy and vasopressors could be the indication.

Approximately 80%–90% of serum cortisol is bound to CBG and albumin. The changes in the concentration of these carrier proteins can affect the concentration of the bound and unbound fraction of cortisol. CBG has a high affinity for cortisol, but has a low capacity to bind it. CBG is saturated at a cortisol level of approximately 690 nmol/L.11,18 When CBG becomes saturated, the remaining cortisol binds to albumin or circulates as a free active fraction of cortisol. In our study, low serum total cortisol was not associated with low CBG, as found in former studies,13 but high calculated free cortisol may be caused by low CBG or saturation of CBG. It must be considered that CBG levels vary widely among subjects under normal conditions as well,19 but especially in critical illness. Our study shows that no patient who fulfilled the criteria (calculated free cortisol <22 nmol/L) of absolute adrenal insufficiency died. If septic patients benefit from small-dose corticoid treatment despite high levels, this implies that tissues do not respond normally to cortisol or exogenous steroids. This has been shown by Molijn et al.20 who suggested that in sepsis and septic shock there might be a decreased affinity of glucocorticoid receptors to glucocorticoids. They also stated that during critical illness, there might be peripheral adaptation of glucocorticoid receptor number and affinity due to activation of the hypothalamopituitary-axis, and that hyperthermia may modify this response.

Our study has some limitations. First, we did not use an ACTH test in assessing the adrenal function. The role of this test is controversial, however. Increased mortality in patients with relative adrenal insufficiency assessed by the ACTH test has been published.1 The debate over interpretation of the results of this laboratory test is increasing, because some concern has been raised about the reproducibility of the ACTH stimulation test in septic patients.16 If an ACTH test would have been performed for patients with high serum cortisol concentrations and an impaired response would have been detected, it may have told us that the reserves of the adrenal gland were exhausted, rather than indicating insufficiency per se. Notably, the ACTH test does not directly test the hypothalamic–pituitary axis, but rather the reaction of the adrenal gland to ACTH. Second, the time of blood sampling was not standardized or predefined. However, it seems that the diurnal variation of serum cortisol disappears in septic shock,21 and therefore this may not have affected our results. Because of early cortisol substitution for septic patients in many hospitals, it was not possible to obtain blood samples for cortisol in a high number of patients before cortisol treatment.

We used the Coolens method12 to calculate serum free cortisol. This method has been shown to be reliable in patients with severe sepsis and septic shock8: Ho et al. compared serum free cortisol measurement with time-consuming and expensive equilibrium dialysis and ultracentrifugation. No clinically relevant differences from the Coolens method were detected. However, Vogeser et al.22 showed that despite a good correlation of measured and calculated serum free cortisol there may be a significant mean percentage difference between both methods and a significant individual difference. Direct measurement of serum free cortisol is not routinely available in our laboratory. Furthermore, calculating serum free cortisol may be a practical tool for almost every laboratory.

We conclude that, in severe sepsis and septic shock, survivors have lower calculated serum free cortisol concentrations than nonsurvivors. However, calculated free cortisol concentrations correlate well with total cortisol concentration, and free cortisol calculation does not predict unfavorable outcome better than total cortisol levels. Clinically, calculation of free cortisol does not help to identify patients who would benefit from corticoid treatment in severe sepsis and septic shock.

	ACKNOWLEDGMENTS

 
Participants in the FINNSEPSIS study:

Satakunta Central Hospital: Vesa Lund; Savonlinna Central Hospital: Markku Suvela; Keski-Suomi Central Hospital: Raili Laru-Sompa; Mikkeli Central Hospital: Heikki Laine; Pohjois-Karjala Central Hospital: Sari Karlsson; Seinäjoki Central Hospital: Kari Saarinen; Etela-Karjala Central Hospital: Seppo Hovilehto; Päijät-Häme Central Hospital: Pekka Loisa; Kainuu Central Hospital: Tuula Korhonen; Vaasa Central Hospital: Pentti Kairi; Kanta-Häme Central Hospital: Ari Alaspää; Lappi Central Hospital: Outi Kiviniemi; Keski-Pohjanmaa Central Hospital: Tadeusz Kaminski; Kymenlaakso Central Hospital: Jussi Pentti, Seija Alila; Helsinki University Hospital: Ville Pettilä, Marjut Varpula, Marja Hynninen; Helsinki University Hospital (Jorvi): Tero Varpula; Helsinki University Hospital (Peijas): Rita Linko; Tampere University Hospital: Esko Ruokonen, Pertti Arvola; Kuopio University Hospital: Ilkka Parviainen; Oulu University Hospital: Tero Ala-Kokko, Jouko Laurila; Länsi-Pohja Central Hospital: Jorma Heikkinen.

	Footnotes

 
Accepted for publication February 15, 2008.

Supported, in part, by a grant from the Päivikki and Sakari Sohlberg Foundation, Helsinki, Finland, and a Kuopio University Hospital Grant.

Reprints will not be available from the author.

	REFERENCES

Top Abstract Introduction METHODS RESULTS DISCUSSION REFERENCES

 

1. Annane D, Sebille V, Charpentier C, Bollaert PE, Francois B, Korach JM, Capellier G, CohenY, Azoulay E, Troche G, Chaumet-Riffaut P, Bellissant E. Effect of treatment with low doses of hydrocortisone and fludrocortisone on mortality in patients with septic shock. JAMA 2002;288:862–71[Abstract/Free Full Text]
2. Annane D, Sebille V, Troche G, Raphael JC, Gajdos P, Bellissant E. A 3-level prognostic classification in septic shock based on cortisol levels and cortisol response to corticotropin. JAMA 2000;283:1038–45[Abstract/Free Full Text]
3. Cooper MS, Stewart PM. Corticosteroid insufficiency in acutely ill patients. N Engl J Med 2003;348:727–34[Free Full Text]
4. Briegel J. Hydrocortisone and the reduction of vasopressors in septic shock: therapy or only chart cosmetics? Intensive Care Med 2000;26:1723–6[Web of Science][Medline]
5. Rhen T, Cidlowski JA. Antiinflammatory action of glucocorticoids—new mechanisms for old drugs. N Engl J Med 2005;353:1711–23[Free Full Text]
6. Lipiner-Friedman D, Sprung CL, Laterre PF, Weiss Y, Goodman SV, Vogeser M, Briegel J, Keh D, Singer M, Moreno R, Bellissant E, Annane D. Adrenal function in sepsis: The retrospective Corticus cohort study. Crit Care Med 2007;35:1012–8[Web of Science][Medline]
7. Annane D, Maxime V, Ibrahim F, Alvarez JC, Abe E, Boudou P. Diagnosis of adrenal insufficiency in severe sepsis and septic shock. Am J Respir Crit Care Med 2006;174:1319–26[Abstract/Free Full Text]
8. Ho J, Al-Musalhi H, Chapman M, Quach T, Thomas P, Bagley C, Lewis J, Torpy D. Septic shock and sepsis: a comparison of total and free plasma cortisol levels. J Clin Endocrinol Metab 2006;91:105–14[Abstract/Free Full Text]
9. Dellinger RP, Carlet JM, Masur H, Gerlach H, Calandra T, Cohen J, Gea-Banacloche J. Surviving Sepsis Campaign guidelines for management of severe sepsis and septic shock. Crit Care Med 2004;32:858–73[Web of Science][Medline]
10. Karlsson S, Varpula M, Ruokonen E, Pettila V, Parviainen I, Ala-Kokko TI, Kolho E, Rintala EM. Incidence, treatment, and outcome of severe sepsis in ICU-treated adults in Finland: the Finnsepsis study. Intensive Care Med 2007;33:435–43[Web of Science][Medline]
11. Bone RC, Balk RA, Cerra FB, Dellinger RP, Fein AM, Knaus WA, Schein RM, Sibbald WJ. Definitions for sepsis and organ failure and guidelines for the use of innovative therapies in sepsis. The ACCP/SCCM Consensus Conference Committee. American College of Chest Physicians/Society of Critical Care Med. Chest 1992;101:1644–55[Web of Science][Medline]
12. Coolens JL, Van Baelen H, Heyns W. Clinical use of unbound plasma cortisol as calculated from total cortisol and corticosteroid-binding globulin. J Steroid Biochem 1987;26:197–202[Medline]
13. Hamrahian AH, Oseni TS, Arafah BM. Measurements of serum free cortisol in critically ill patients. N Engl J Med 2004; 350:1629–38[Abstract/Free Full Text]
14. Moran JL, Chapman MJ, O’Fathartaigh MS, Peisach AR, Pannall PR, Leppard P. Hypocortisolaemia and adrenocortical responsiveness at onset of septic shock. Intensive Care Med 1994; 20:489–95[Web of Science][Medline]
15. Marik PE, Zaloga GP. Adrenal insufficiency during septic shock. Crit Care Med 2003;31:141–5[Web of Science][Medline]
16. Loisa P, Uusaro A, Ruokonen E. A single adrenocorticotropic hormone stimulation test does not reveal adrenal insufficiency in septic shock. Anesth Analg 2005;101:1792–8[Abstract/Free Full Text]
17. Cohen J, Ward G, Prins J, Jones M. Variability of cortisol assays can confound the diagnosis of adrenal insufficiency in the critically ill population. Intensive Care Med 2006;32: 1901–05[Web of Science][Medline]
18. Aron DC, Findling JW, Tyrrell JB. Glucocorticoids & Adrenal Androgens. In: Greenspan FS, Gardner DG, eds. Basic & clinical endocrinology. 6th ed. United States: Lange, 2001; 342–3
19. Dhillo WS, Kong WM, Le Roux CW, Alaghband-Zadeh J, Jones J, Carter G, Mendoza N, Meeran K, O’Shea D. Cortisol-binding globulin is important in the interpretation of dynamic tests of the hypothalamic–pituitary–adrenal axis. Eur J Endocrinol 2002;146: 231–5[Abstract]
20. Molijn GJ, Koper JW, van Uffelen CJ, de Jong FH, Brinkmann AO, Bruining HA, Lamberts SW. Temperature-induced down-regulation of the glucocorticoid receptor in peripheral blood mononuclear leucocyte in patients with sepsis or septic shock. Clin Endocrinol (Oxf) 1995;43:197–203[Medline]
21. Voerman HJ, Strack van Schijndel RJ, Groeneveld AB, de Boer H, Nauta JP, Thijs LG. Pulsatile hormone secretion during severe sepsis: accuracy of different blood sampling regimens. Metabolism 1992;41:934–40[Web of Science][Medline]
22. Vogeser M, Groetzner J, Küpper C, Briegel J. Free serum cortisol during the postoperative acute phase response determined by equilibrium dialysis liquid chromatography–tandem mass spectrometry. Clin Chem Lab Med 2003;41:146–51[Web of Science][Medline]

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