Cortisol Awakening Response

This curve is derived from taking four daily saliva collections – typically done upon waking, before lunch, before dinner and before bed – and charting them on a 24-hour graph.

The resulting curve – also called a four-point cortisol curve or circadian cortisol pattern – reveals cortisol levels throughout the day, allowing the pinpointing of  issues with adrenal gland function.

This pattern shows a normal rise in cortisol production within 30 minutes of waking for the day. Cortisol levels then drop throughout the day, reaching their lowest point at bedtime.

Diurnal Cortisol Patterns with Adrenal HPA Axis Dysfunction

Cortisol production is normally at its highest 30 minutes after waking and declines steadily during the day, reaching its lowest point at bedtime. Those with adrenal gland dysfunction generally have irregularities in their diurnal cortisol curves. Some common examples are shown below.

Overall higher than normal cortisol production throughout the day can result from prolonged stress demands. General symptoms include feeling “tired but wired,” food cravings, insomnia and anxiety.

The pattern for chronic fatigue shows an elevated morning cortisol with levels dropping off rapidly during the day. General symptoms include mid-day energy drop, drowsiness and poor exercise recovery.

The burnout pattern, also commonly called “adrenal fatigue” is really a reflection of low overall cortisol during the day. General symptoms include day-long fatigue, irritability, food cravings, insomnia and exhaustion.

The Cortisol Awakening Response

Sunlight influences the diurnal rhythm and when it becomes scarce, those rhythms can become dysregulated. The adrenal hormone, cortisol, reacts to stressors in the body like inflammation, illness and low blood sugar; however, outside of its first-response job, it follows a very typical diurnal rhythm. It can be measured upon waking and throughout the day with results in saliva that look a lot like the graph below.

Normally, in the morning as the sun begins its ascent, cortisol charts its course toward the highest level of our 24-hour day. Within 30 minutes of waking up, cortisol should continue to rise by about 50% from the waking level. When the mornings are dark, in susceptible individuals the diurnal rhythm of cortisol flattens out and it becomes difficult to shake off sleep and function normally. Another helpful measure of the HPA axis that captures that 50% rise (or absence of it) is called the cortisol awakening response (CAR) which measures cortisol in response to the “stress” of waking.

Here’s a normal CAR — observe the 2^nd black dot in the graph below showing the cortisol level at 30 minutes after the initial waking sample:

Here’s an example of a CAR in someone struggling with SAD:

Notice the morning, noon, evening and night cortisol levels are roughly within normal ranges while the attenuated CAR is the finding of interest. Overall, the defect in cortisol regulation in SAD may be missed if the CAR isn’t assessed along with the diurnal rhythm.