What is the Origin of Diurnal Slope?

The term combines "diurnal," from the Latin diurnalis meaning "of the day," and "slope," a mathematical term describing the gradient or rate of change. Its application in endocrinology originated with the study of circadian rhythms, particularly the daily oscillation of adrenal hormones.

What is the Mechanism of Diurnal Slope?

The mechanism is driven by the suprachiasmatic nucleus (SCN) in the hypothalamus, which acts as the body's master clock, regulating the pulsatile release of ACTH, which in turn stimulates cortisol production. This HPA axis activity is highest upon waking and is then systematically downregulated throughout the day via negative feedback loops, creating the characteristic downward slope in serum or salivary cortisol concentration.

Diurnal Slope

Meaning

A specific pattern of hormonal secretion characterized by a measurable change in concentration over the course of a 24-hour day, often used clinically to assess the hypothalamic-pituitary-adrenal (HPA) axis. This term most commonly describes the typical sharp decline in cortisol levels observed from the morning peak until late evening. A healthy diurnal slope is a key indicator of robust stress response and circadian rhythm integrity.