Circadian variations in melatonin and cortisol in patients with cervical spinal cord injury

In cervical spinal cord injury (CSCI), afferent and efferent circuits that influence the basal production of melatonin and cortisol may be disrupted and hence disrupt the basal functions of human physiology. Therefore, the aim of this study was to assess circadian changes, if any, in serum cortisol and melatonin in patients with CSCI.

Serum levels of cortisol and melatonin were measured at 6-h intervals of the day (0600, 1200, 1800 and 0000 hours) in 22 CSCI patients, as well as 22 healthy controls.

Significantly higher melatonin levels were observed in the patient group in morning hours, whereas a significantly lower level of melatonin was found during the night time in the patient group than in the control group. Moreover, significantly higher values were obtained in the evening and night time serum cortisol levels among the patients compared with controls. Further, when the mean values of cortisol throughout the day were tested among patient and control groups similar circadian rhythm was found. The only difference being that serum cortisol declined much more in controls in evening and night samples as compared with CSCI patients.

We conclude that circadian variations exist in the circulating levels of serum cortisol and melatonin in patients with CSCI. Low levels of melatonin secretion during night may contribute to the pervasive sleep disruption and increased pain perception.