Cortisol: More Than a Stress Hormone
Most people associate cortisol with stress. But cortisol is involved in much more than the familiar fight-or-flight response.
It participates in glucose regulation, metabolism, immune activity, blood-pressure maintenance, and the body's daily biological rhythms. Persistently elevated cortisol, as occurs in Cushing syndrome, may contribute to symptoms including:
Unexplained weight gain, particularly around the abdomen
Muscle weakness and fatigue
Elevated blood pressure and blood sugar
Skin changes and easy bruising
Bone loss
Mood and concentration changes
Menstrual and other reproductive changes
Reduced sex drive
Greater susceptibility to infections
Of course, these symptoms can occur for many reasons. Having one or several does not establish that cortisol is elevated.
But understanding cortisol's broad influence may help explain why endocrine disorders can affect so many different systems.
Why Do We Wake Between 2 and 4 A.M.?
This question particularly interested me because it appeared repeatedly in the experiences people shared with us.
Cortisol follows a daily rhythm. In most people who sleep at conventional hours, cortisol is relatively low during the early part of the night and begins increasing toward morning, helping prepare the body for waking.
But cortisol is not the only participant.
Blood glucose can fall during the night. When that happens, the body may release adrenaline and other hormones to help restore glucose. The resulting response can awaken someone suddenly, sometimes leaving them unusually alert.
Sleep apnea, restless legs, medications, pain, stress, and environmental disturbances can also interrupt sleep.
In other words, waking at 3 a.m. does not necessarily mean that cortisol is too high.
Nevertheless, the repeated reports from our volunteers raise an interesting question: might changes in stress-hormone regulation contribute to this pattern in some individuals?
We believe the question deserves further investigation.