The media has dubbed cortisol “the stress hormone”, and although it is one of the main hormones that drive our fight and flight response, it does so much more than that. To understand the role of cortisol, we need to understand that what it effectively does is to stimulate several processes that collectively help increase the concentration of glucose in the blood. Therefore, our cortisol levels increase when we need to increase our body’s energy consumption, such as when we are learning, waking up in the morning, fighting an infection or, yes, when we are in a stressful situation.
We first need to understand how cortisol is able to influence our body’s energy supply. When we consume food, our stomach breaks down the food into glucose and releases it into our bloodstream. To keep our body running smoothly, 60-100 mg/dl of glucose is needed in the blood. When our blood glucose rises above this, the pancreas produces insulin, which acts as the key that opens the door of our muscle and fat cells’ storage rooms. Any excess glucose can therefore be stored in our muscles and fat cells to be used in the future when glucose may be needed. In times when we need our blood glucose levels to increase, cortisol will be released, as it overrides insulin's ability to store the additional glucose in the blood, keeping the blood glucose levels elevated.
Due to cortisol’s role in managing blood glucose levels, we can start to see why cortisol is not only an important hormone in times of stress. It also plays an important function in managing our circadian rhythm as well as our long-term memory.
Cortisol levels are highest during waking hours and starts to fall in the evening. When we are sleeping, our cortisol levels are at their lowest, while physical repairs take place in our body. In the early morning hours, our cortisol levels start to rise, and it peaks when we wake up to help us get going. Be mindful then about managing this cycle by going to bed and getting up around the same time every day. If this cycle falls out of balance, it becomes hard to fall asleep at night as your blood glucose levels may still be elevated, while you may feel like you have no energy to get up in the mornings.
And finally, but perhaps most interestingly, cortisol has been shown to play a key role in both memory retrieval and memory consolidation. Cortisol levels’ effects on memory consolidation can be thought of as an inverted "U" on a graph, where moderate levels enhance memory consolidation, while too much or too little cortisol impairs memory formation and consolidation. Therefore, during periods when we may experience mild stress, we are best positioned to form LT memories, but it has been shown that during periods where cortisol levels are elevated for longer than one hour, memory consolidation is inhibited.
Several studies have shown, however, that exposure to cortisol also impairs memory retrieval from the hippocampus, even in situations where we experience short term stress. It has further been shown that the amygdala plays a key role in using states of elevated cortisol levels to enhance memory retrieval from the parts in our brain that store habitual memories, causing us to fall back on our habits, even if it is not the best response.
By understanding cortisol we can more effectively manage the important role it plays in our lives, because as you can now clearly see it is not just a stress hormone but does so much more to help you live your life to the fullest.
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