What is Morning Cortisol (Saliva)?
Cortisol secretion follows a circadian rhythm driven by hypothalamic corticotrophin-releasing hormone and pituitary ACTH. Under normal conditions the hypothalamic–pituitary–adrenal axis generates a sharp morning peak 30–45 minutes after waking (the cortisol awakening response), followed by a decline through midday and afternoon to a nadir in the late evening. Salivary cortisol reflects the unbound, biologically active fraction and tracks the dynamics of this diurnal pattern more faithfully than a single serum sample.