Sleep deprivation disrupts which physiological pattern related to stress?

• A. Blood glucose regulation
• B. Melatonin production
• C. Cortisol diurnal rhythm
• D. Sleep-wake cycle

Answer: (C)

Sleep loss activates our stress response system, which is governed by the cortisol diurnal rhythm. Cortisol normally rises in the early morning to help wakefulness and energy, then gradually declines across the day, reaching a low point at night. When sleep is deprived, this pattern becomes disrupted: cortisol can stay elevated later into the day or rise at night, and the typical morning peak may be blunted or delayed. This reflects altered HPA axis regulation and circadian signaling, highlighting how stress physiology is tightly linked to cortisol timing. While sleep deprivation can influence other processes like glucose handling or melatonin signaling, the pattern most clearly tied to stress physiology and most disrupted by sleep loss is the diurnal rhythm of cortisol.