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Cortisol is a ‘master’ hormone produced by the adrenal cortex (the outer part of the adrenal gland that produces hormones, including stress hormones) and is released in response to chronic or repeated stress and low blood glucose concentrations. Its function in the body is to increase blood sugar through gluconeogenesis (by metabolising proteins into sugar) to suppress the immune system; it also decreases bone formation, diverting the process into gluconeogenesis in favour of osteogenesis (bone formation).

It is also activated in fasting, and calorie restriction, especially carbohydrate restriction. This is one of the body’s protective responses to possible starvation.

Chronic release of cortisol will eventually lead to chronic rises in blood glucose with overstimulation of insulin production and the eventual development of glucose intolerance, insulin resistance, beta cell (the cells that produce insulin) exhaustion, and, ultimately, can lead to diabetes. Prolonged periods of raised cortisol results in muscle loss, increase in belly fat, suppression of the immune system with increased risk of infections, thinning of the skin and premature ageing, osteoporosis and bone fractures, fragility of blood vessels, high blood pressure, heart disease and an increased risk of cancer through weakening the T-cell and natural killer cells (these are part of the immune system that look for early changes in cells that may lead to cancer, and destroy them).

Cortisol also inhibits collagen and elastin production, thereby weakening the infrastructure of skin, bones, blood vessels and all of the tissues in the body; it slows down and inhibits wound healing; and it has an effect on the kidneys by increasing sodium retention and potassium excretion, which can result in high blood pressure. Cortisol increases the gastric excretions, and decreases the gastric defences, thereby increasing the risk of gastric and duodenal ulcers and bleeding. Changes in the normal daily patterns of cortisol can lead to sleep disorders, mood and anxiety disorders, and depressive disorders. Chronic cortisol elevation can also decrease fertility.

High cortisol also interferes with thyroid function, and can lead to an underactive thyroid response. The body shape changes to resemble a ‘lemon on sticks’ as a result of muscle loss in the arms and legs, and excess belly fat.

A 24-hour saliva test to assess your personal levels of stress and adrenal fatigue may be useful if you’re concerned (unfortunately this is not available on the NHS, and has to be arranged privately). Fortunately, your cortisol levels can be managed using meditation, supplementation, nutrition and exercise.