Cortisol: The Stress Hormone

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What is Cortisol?

Cortisol, a glucocorticoid produced by the adrenal cortex, is commonly referred to as the stress hormone. Normal cortisol production occurs as a repeated rhythm – highest in the morning dropping quickly to very low values late at night, every day of our life. We cannot live without cortisol, but we also cannot tolerate too much of it. Diet can play an important role in shifting cortisol levels.


During particularly stressful events, extra cortisol is released to handle the situation by controlling nutrients our bodies need. The down side is that if stress levels stay chemically high, so do cortisol levels which, long term, can hurt our health by decreasing our immunity and softening our bones.


Cortisol is one of our body’s major stress hormones. Under normal conditions, cortisol behaves in a way that prepares our body to deal with stress by breaking down protein and raising blood sugar levels. But if cortisol levels stay too high for a long time, then it is not very favourable situation. The short-term benefits become long term hazards. Suddenly we are faced with a steady stream of a hormone that, in the long term, can break down our muscles and bones as well as reduce the efficiency of our protective immune system.

The perfect cortisol response to stress is a sharp rise in levels to help our body accommodate. Then, when the stress is under control, there should be a rapid drop down to low resting levels. The problem arises when cortisol doesn’t drop quickly, and when it does drop, the resting levels are too high for optimal hormonal health.

For professionals, care must be taken measuring cortisol levels. When evaluating the levels of exercising subjects, even if there is a matched control group, it is important to take into consideration that cortisol levels drop by 90% (a process called diurnal variation) over the course of a day and that the drop is steepest during the morning hours. Some researchers suggest measuring each subject’s daily cortisol pattern on a non-test day so as to have a direct comparison of the ‘level drop rate’ for each individual.


Cortisol can respond to either psychological or physiological stress, so it makes sense that some forms of more active exercise will increase cortisol levels. In athletes, a significant increase in cortisol levels requires exercising 20 minutes at intensity levels of 60% or higher of the predicted maximum heart rate. The longer and more intense the workout, the higher the cortisol levels. But there is a limit as over training by competitive athletes and fitness enthusiasts is associated with markers of distress including elevated cortisol levels.

Thirty minutes of moderate cycling in men results in elevated cortisol levels along with pronounced muscle activation. In another male study comparing weight lifters to aerobicisers, each had elevated cortisol levels following exercise that disappeared within 1-2 hours post-exercise.


In trained women, a volleyball game did not raise cortisol levels but a handball game did. It could be that the intensity of the volleyball game did not reach the exercise level needed to physiologically increase cortisol levels or that there was psychological stress associated with a competitive one-on-one handball game. In another female study, untrained women took part in a 12-week resistance training program which included circuit training 4 days a week. By week 12 their resting cortisol levels were lower.


Exercise less intense than that needed to raise cortisol levels of younger more active individuals may trigger increased cortisol secretion in sedentary or older adults. After exercise, cortisol usually decreases rapidly and reaches resting levels within hours. But with older adults, sustained exercising-induced high cortisol levels can mask other serious pathological conditions such as infection or severe psychological stress. It thus becomes imperative and important for senior exercisers to let their doctors know if they have been recently exercising so there is no confusion as to the cause of elevated cortisol levels.


Increased production of cortisol in older adults has been shown to result in diminished immune function, and, consequently, higher rates of respiratory and other infections. So, the exercise prescription given to the older individual to help maintain good health must be balanced with the knowledge that there could be an increased risk of infection.

Increased cortisol levels, no matter what the cause, have been shown to inhibit the production of testosterone, which doesn’t help the already flagging level in many midlife and older males.

There are some exercise programs that do not increase cortisol levels and, in fact, decreases them. Both land stretching and water exercise in a group of older men and women not only decreases cortisol levels but also decreases anxiety. Mind-body exercises such as yoga and tai chi incorporate features like precisely choreographed movements, breathing regulation, meditation and balance. Several studies have found that both methods can positively influence flexibility, hypertension, ventilation and cardiovascular performance. It may also lower cortisol levels, along with these accompanied changes.

It is important to have the knowledge and awareness about the right level of Cortisol in body.