What is the Origin of Daytime Cortisol Elevation?

This descriptive term is rooted in endocrinology and chronobiology, combining the hormone's name, "cortisol," with the temporal descriptor "daytime" and the physiological event "elevation." It describes a key characteristic of the ultradian and circadian rhythm of this adrenal hormone. The CAR component was specifically identified as a distinct, anticipatory rise.

What is the Mechanism of Daytime Cortisol Elevation?

Cortisol secretion is tightly regulated by the Hypothalamic-Pituitary-Adrenal (HPA) axis, with the suprachiasmatic nucleus driving the circadian rhythm. Upon waking, the CAR is triggered by a surge in Adrenocorticotropic Hormone (ACTH), causing the adrenal glands to release a pulsatile burst of cortisol. This mechanism prepares the body metabolically and neurologically for the anticipated activity and energy expenditure of the day. Proper elevation supports gluconeogenesis and immune surveillance.

Daytime Cortisol Elevation ∞ Area

Daytime Cortisol Elevation

Meaning

Daytime cortisol elevation refers to the naturally occurring, rhythmic increase in the glucocorticoid hormone cortisol during the waking hours, particularly the pronounced Cortisol Awakening Response (CAR) in the early morning. This physiological pattern is essential for mobilizing energy stores, modulating immune function, and promoting alertness to meet the demands of the active phase. Clinically, assessing the magnitude and timing of this elevation is crucial for evaluating HPA axis integrity and stress resilience.