SHORT-TERM NIGHT-SHIFT WORKING MIMICS THE PITUITARY-ADRENOCORTICAL DYSFUNCTION IN CHRONIC FATIGUE SYNDROME

The purpose of this study was to determine whether a short period (5 d ays) of night-shift work affected the pituitary-adrenal responses to C RH. Ten nurses (8 female and 2 male; age 28.1 +/- 1.7 yr: mean +/- SEM ) working at the Royal Liverpool University Hospital, and who regularl y undertook periods of night and day shift work were enrolled. Measure ments were made of basal ACTH and cortisol concentrations, and their r esponses to iv ovine CRH (1 mu g(.)kg(-1)). Basal ACTH concentrations were higher during the night shift than during the day shift (12.9 +/- 5.1 pmol(.)L(-1) vs. 4.7 +/- 1.2 pmol(.)L(-1), P < 0.01), whereas cor tisol concentrations were lower (551 +/- 48 nmol(.)L(-1) vs. 871 +/- 1 32 nmol(.)L(-1), P < 0.01). After CRH injection, ACTH concentrations r emained consistently higher during the night shift, but the integrated increase in ACTH concentration was lower (P < 0.05) than during the d ay shift. Conversely, the increase in cortisol concentration was great er during the night shift than the day shift (283 +/- 53 nmol(.)L(-1) vs. 134 +/- 41 nmol(.)L(-1), P < 0.05). We conclude that the pituitary -adrenal responses to CRH are markedly disrupted after only 5 days of nighttime work. These abnormalities mimic those previously observed in patients with chronic fatigue syndrome. Neuroendocrine abnormalities reported to be characteristic of chronic fatigue syndrome may be merel y the consequence of disrupted sleep and social routine.