What is the Origin of Diurnal Cortisol Rhythm?

This concept originates from the fields of chronobiology and endocrinology, merging "diurnal," relating to the daytime, with "rhythm," indicating a recurrent, measurable biological pattern. The rhythm is a key component of the body's internal clock, which is primarily regulated by the suprachiasmatic nucleus in the hypothalamus.

What is the Mechanism of Diurnal Cortisol Rhythm?

This critical hormonal cycle is centrally governed by the Hypothalamic-Pituitary-Adrenal (HPA) axis, which coordinates the timing of cortisol release in response to light and the sleep-wake cycle. A deviation, such as a flattened or inverted rhythm, clinically signals HPA axis dysregulation, often compromising the body's ability to manage chronic stress and maintain metabolic homeostasis.

Diurnal Cortisol Rhythm ∞ Area ∞ Library 3

Diurnal Cortisol Rhythm

Meaning

The Diurnal Cortisol Rhythm describes the characteristic, predictable pattern of cortisol secretion over a complete 24-hour period in a healthy human. This rhythm is typically defined by a sharp, robust increase immediately upon waking, followed by a steady, gradual decline throughout the day, reaching its nadir around midnight. This precise oscillation is fundamentally vital for maintaining the circadian clock and effectively regulating energy balance and immune function.