Earlier in activity times, changes happen in

Earlier studies have been shown a shift in activity times, changes happen insleep period and feeding behavior together influence circadian control of theendocrine system (16,17)In this study, secretion pattern cortisol is similar to the diurnalryhtem of cortisol seen in previous studies (3,12) with peak levels occurringat early morning (06.00 p.m.) and sleep disruption had no significant effect onthis pattern. The results of Scheer et.

al (2009) study showed, the cortisol secretion pattern is more influenced by the internaldaily rhythms rather than behavior (fasting-feeding and sleep/wake) cycles (18).The study Fumihisa et al. (2013) showed that nightshift (from 0:00 to 8:00) had not effect on circadian rhythm in male nurses.

Inaddition,  the concentration ofcortisol  in night shift did not differfrom that of the control group (19). Also in our study, the average concentrationof cortisol throughout 24 h  was notsignificantly higher in the disrupted sleep group than the control group.In agreement withour study, a previous study,  did not show a significant circadian rhythmfor acylated ghrelin in  the normalsubjects that take 3 meals in a day (14). It seemsthat the nutritional state of the person is effective on ghrelin secretionpulses. Fasting augmented all parameters of ghrelin pulsatile secretion (20). In contrast to our study, some previous studies havereported circadian rhythm for ghrelin (13). This can be due tomethodological differences that prevented comparison  this study with other works.

1- the number of blood sampling: In ourstudy, The number of blood sampling was 6 times during 24 hours. Whereas in otherworks were between 24-72  during 24 hours(14,13,21). 2- Age and sex. Most previous studiesthat reported circadian rhythm for ghrelin have been done in female subjects anda very large age range (13,21).

3-sleep and sleepdeprivation condition. In most previous studies, effects of sleep on a diurnalor nocturnal pattern of ghrelin secretion investigated in the laboratoryconditions not mimicking “real life.In conclusion, Sleep deprivation has no significanteffect on the diurnal pattern of cortisol. In addition, ghrelin does not show acircadian rhythm. Limitations:The small number of subjects and lownumber sampling over 24 h are limitations.