Normal salivary cortisol and NK cell function in adolescents with chronic fatigue syndrome following infectious mononucleosis

Background: Chronic fatigue syndrome (CFS) is a complex condition involving severe fatigue and disabling musculoskeletal and cognitive symptoms. We reported that 6, 12 and 24 months following infectious mononucleosis (IM), 13%, 7% and 4% of adolescents, respectively, met criteria for CFS. Whether endocrinologic or immunologic dysfunction accompanies CFS is unclear. Objectives: To determine if salivary cortisol levels or NK cell percentage and function 6, 12 and 24 months following IM in adolescents who met criteria for CFS and recovered, matched controls differ. Patients and Methods: Nine adolescents with CFS and nine matched, recovered controls had morning and nighttime salivary cortisol as well as NK cell number and function measured blindly 6, 12 and 24 months following IM. Results: Three subjects with CFS had a depressed morning salivary cortisol; one control subject had a single depressed nighttime cortisol. There was no difference in NK cell percentage or decreased function between cases and recovered controls. Conclusions: We found little evidence of depressed salivary cortisol levels and no decreased NK cell function in adolescents with CFS following IM.