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Cortisol Diurnal Pattern

Meaning

The Cortisol Diurnal Pattern describes the predictable, time-dependent fluctuation of circulating cortisol concentrations throughout a 24-hour cycle in a healthy individual. Clinically, this pattern is characterized by a peak, often termed the Cortisol Awakening Response (CAR), occurring shortly after waking, followed by a steady decline toward nadir levels late in the sleep period. Deviation from this established rhythm, such as flattened curves or elevated nighttime levels, strongly indicates HPA axis dysregulation. Assessing this pattern provides a superior diagnostic measure compared to single-point cortisol testing.