What is the Origin of Morning Cortisol Spike?

This term is a cornerstone of chronobiology and clinical endocrinology, representing the most dynamic phase of the HPA axis's 24-hour cycle. It is a practical, descriptive name for the rapid rise in the stress hormone that initiates the waking state, with its magnitude and timing serving as a key biomarker for stress adaptation capacity.

What is the Mechanism of Morning Cortisol Spike?

The spike is initiated by the Suprachiasmatic Nucleus (SCN) signaling the hypothalamus and pituitary gland to release ACTH, which stimulates the adrenal glands. This hormonal surge rapidly increases blood glucose availability and enhances alertness by acting on glucocorticoid receptors in the brain. A healthy spike is essential for establishing Post-Wake Arousal Stability and driving optimal Daytime Productivity.

Morning Cortisol Spike ∞ Area

Morning Cortisol Spike

Meaning

The Morning Cortisol Spike, clinically known as the Cortisol Awakening Response (CAR), is the sharp, rapid increase in circulating cortisol concentration that occurs immediately upon or just before waking from sleep. This physiological event is a critical component of the Cortisol Diurnal Variation, serving to terminate the nocturnal fast, mobilize energy reserves, and prepare the body for the metabolic and cognitive demands of the day. A robust spike is a hallmark of a healthy, resilient hypothalamic-pituitary-adrenal (HPA) axis.