Under the direction of the hypothalamus and pituitary, and controlled by a negative feedback loop, the zona fasciculata of the adrenal cortex is stimulated to produce cortisol in response to circadian peaks and troughs in ACTH synthesis in addition to various types of stressors such as emotional/psychological, physical (injury, exercise), chemical, pathological (viruses, bacteria, etc.).
The feedback loop is commonly referred to as the hypothalamic-pituitary-adrenal (HPA) axis.
In a normal nonstressed state cortisol production is at its highest upon waking and declines steadily during the day, reaching its lowest point at bedtime.
Cortisol has a wide range of effects on mind and body and interacts with the reproductive, thyroid and immunological systems. As part of the stress response, it prepares the body for “fight or flight” by regulating epinephrine (adrenaline) biosynthesis, and in doing so it can suppress the production of other hormones, including those involved with reproduction, and some immune functions.
Salivary cortisol measurements are considered the gold standard in testing stress, in screening for Cushing’s disease, and in evaluations of adrenal insufficiency, such as Addison’s disease.
Cortisol (morning)
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