Endocrine Abstracts

Patients with Cushing’s syndrome have a poor quality of sleep. However, little is known about their timing of sleep as regulated by the circadian clock, the so called-chronotype. Considering that patients with Cushing’s syndrome lose their rhythmic circadian cortisol secretion and that corticosteroids act as synchronizer of the circadian clock in cells, aim of the study was to determine whether patients with Cushing’s syndrome alter the timing of their sleep compared to a control population and, if so, whether this persists after remission of the disease. To this aim, we administered the Munich Chronotype Questionnaire (MCTQ) and collected data from 12 patients with Cushing’s syndrome (mean age 45 ± 14), 58 patients in remission (mean age 48 ± 12) and 26 controls with no history of hypercortisolism (mean age 45 ± 12). The MCTQ analysis revealed that patients with Cushing’s syndrome have a significantly shorter weekly sleep duration vs. patients in remission (05:10 ± 01:56 vs. 06:43 ± 01:36 P = 0.019). The Cushing’s patients woke earlier on both workdays and work-free days vs. controls (P = 0.001 and P = 0.005 respectively) and vs. patients in remission (P = 0.011 and P = 0.009 respectively). The mean wake time of Cushing’s patients on workdays and work-free days was at 0443 ± 0117 h and 0535 ± 0145 h respectively, while for control and remission groups sleep ended at 0618 ± 0119 h and 0604 ± 0120 h respectively on workdays and at 0721 ± 0140 h and 0717 ± 0137 h respectively on work-free days. The mid-sleep-time on free days “MSF” was earlier in patients with Cushing vs controls (P = 0.051) and vs remission (P = 0.094). The mid-sleep-time on free days corrected for the “oversleep” due to the sleep deprivation that people accumulate during the workdays (Midsleep time on Free days sleep-corrected, MSFsc) was significantly earlier in patients with Cushing vs. controls (P = 0.035). These data suggest that patients with Cushing’s syndrome have an early chronotype due to wake-up time and that this alteration could recover after remission. It is noteworthy that the mean sleep-offset of the controls is almost the same compared to that of patients in remission. The MCTQ could be a new instrument in the complex and challenging diagnostic approach to Cushing’s syndrome, and in the detection of recurrence. Based on our findings, we suggest that information on sleep timing should be routinely collected on patients suffering from Cushing’s syndrome. This data will contribute to understanding how the homeostat and the circadian clock interact to yield consolidated sleep at a particular phase according to the individual.