What is the Origin of Post-Sleep Cortisol Flattening?

The term is derived from clinical endocrinology, where the "flattening" describes the deviation from the expected, steep rise in the cortisol curve measured immediately after sleep. The CAR itself is a well-established physiological marker for Hypothalamic-Pituitary-Adrenal (HPA) axis function. Understanding this blunted profile is crucial for assessing chronic stress adaptation and resilience.

What is the Mechanism of Post-Sleep Cortisol Flattening?

This flattening is thought to result from chronic, low-grade HPA axis overstimulation, leading to a compensatory downregulation or exhaustion of the system's responsiveness. The diminished cortisol pulse upon waking fails to adequately prime the body's metabolic and immune systems for the day's challenges. This suboptimal hormonal signal can negatively impact energy levels, immune surveillance, and overall stress resilience.

Post-Sleep Cortisol Flattening ∞ Area

Post-Sleep Cortisol Flattening

Meaning

Post-Sleep Cortisol Flattening refers to an abnormal or suboptimal profile of the Cortisol Awakening Response (CAR), characterized by a significantly reduced or absent sharp increase in cortisol concentration upon waking. A flattened CAR is clinically recognized as a potential indicator of chronic HPA axis dysregulation, often associated with burnout, chronic fatigue, or excessive allostatic load. This blunted response suggests an inability to mount a healthy, adaptive stress response to the demands of the day.