[Note: Cortisol is a stimulant/stress-response hormone. Its daily rhythm normally peaks in early morning and is lowest at night. The cycle in these ME/CFS patients was 'flattened' – meaning lower than normal in the AM, higher than normal at night.]
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. [Cortisol is produced by the adrenal gland and plays a role in activity of the immune system.]
Methods: 28 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. [Note: A previous article by this team reported low morning cortisol but suggested that the finding applied to females only. Asked if the present study found a gender difference, the authors replied: "Unfortunately, we cannot make any conclusive statements about sex differences in our Wichita analyses (published in Psychosomatic Medicine) due to the small sample size. Out of the 17 CFS subjects providing full sets of cortisol samples over the course of the day, only 3 were men. We may assume that the flattened cortisol pattern was driven by the mostly female CFS cases, but we cannot be sure without examining more male subjects. We will be able to address this question in future studies." See also the CFIDS Association's comments on the present article.]
Source: Psychosomatic Medicine, April 1, 2008; 70(3):298-305. Nater UM, Youngblood LS, Jones JF, MD, Unger ER, Miller AH, Reeves WC, Heim C. Chronic Viral Diseases Branch, Coordinating Center for Infectious Diseases, CDC; Department of Psychiatry & Behavioral Sciences, Emory University School of Medicine, Atlanta, Georgia, USA. [E-mail: firstname.lastname@example.org]