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Alterations in diurnal cortisol rhythms in a population-based sample of cases with chronic fatigue syndrome.

Nater UR, Solomon-Youngblood L, Jones JF, Unger ER, Miller AH, Reeves WC, Heim C.
Psychosomatic Medicine 70:298-305, 2008. doi:10.1097/PSY.0b013e3181651025.

Summary

The pathophysiology of CFS involves abnormal response to stress. This paper confirms our findings in Georgia of alterations in cortisol rhythm in persons with CFS compared to well controls (to view this study: http://www.cdc.gov/cfs/publications/clinical_10.htm). This is extremely important because now two independent population based studies have shown persons with CFS have a blunted normal daily cortisol rhythm compared to well controls. This paper analyzed data from the Wichita Clinical Study (to view this study: http://www.cdc.gov/cfs/publications/casedef_10.htm). Specifically, we measured cortisol in saliva during participants' first hospital day, immediately upon awakening, at 8.00 AM, noon, 4.00 PM, 8.00 PM and at bedtime. Salivary cortisol represents free biologically active cortisol and is readily collected. Persons with CFS and well controls showed an initial increase in salivary cortisol concentrations on awakening, followed by a continued decrease through the end of the day. The initial salivary cortisol concentration was lower in the CFS group, the rate of decrease during the day was significantly less rapid, and the concentration of salivary cortisol at bedtime was higher in persons with CFS than controls. This suggests that dysregulation of the normal daily cycle of cortisol might be related to fatigue symptoms.

Abstract

Objective: To examine diurnal salivary cortisol rhythms and plasma IL-6 concentrations in persons with chronic fatigue syndrome (CFS), persons not fulfilling a diagnosis of CFS (we term them cases with insufficient symptoms or fatigue, ISF) and nonfatigued controls (NF). Previous studies of CFS patients have implicated the hypothalamic-pituitary-adrenal axis and the immune system in the pathophysiology of CFS, although results have been equivocal.

Methods: Twenty-eight people with CFS, 35 persons with ISF, and 39 NF identified from the general population of Wichita, Kansas, were admitted to a research ward for 2 days. Saliva was collected immediately on awakening (6:30 AM), at 08:00 AM, 12 noon, 4:00 PM, 8:00 PM and at bedtime (10:00 PM) and plasma was obtained at 7:30 AM. Salivary cortisol concentrations were assessed using radioimmunoassay, and plasma IL-6 was measured using sandwich enzyme-linked immunosorbent assay.

Results: People with CFS demonstrated lower salivary cortisol concentrations in the morning and higher salivary cortisol concentrations in the evening compared with both ISF and NF groups indicating a flattening of the diurnal cortisol profile. Mean plasma IL-6 concentrations were highest in CFS compared with the other groups, although these differences were no longer significant after controlling for BMI. Attenuated decline of salivary cortisol concentrations across the day and IL-6 concentration were associated with fatigue symptoms in CFS.

Conclusions: These results suggest an altered diurnal cortisol rhythm and IL-6 concentrations in CFS cases identified from a population-based sample.

Page last modified on September 1, 2008

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