Blog — cortisol awakening response

  By Dr. Tracy Tranchitella, ND (ZRT Laboratory) The Cortisol Awakening Response (CAR) is the predictable rise in cortisol within the first hour of awakening. There are two events that contribute to this dynamic rise in morning cortisol. The first is in response to adrenocorticotropic hormone output from the pituitary as a part of the normal circadian activities of the hypothalamic–pituitary–adrenal (HPA) axis with involvement from the sympathetic nervous system. The second occurs in response to exposure to daylight with the activation of the suprachiasmatic nucleus in the hypothalamus, which happens within 30-45 minutes after awakening and can increase cortisol...

Cortisol should increase around %50 in the first 30 minutes on awakening then start to progressively drop the remainder of the day. Three, rather than one, early morning collections are what is needed to accurately assess the CAR; one immediately on waking, one 30 minutes later, and another at 1 hour. Diurnal Rhythm Assessment Thirty minutes after awakening from a good night's sleep, cortisol levels are at the highest they'll be all day. Following the morning peak, cortisol levels then fall to less than half that peak level by noon. They continue to drop to very low levels at night where...