Cortisol is a steroid hormone produced by the adrenal glands, and is essential for life. The functions of cortisol are:

  • releases glucose from protein into the bloodstream
  • facilitates fat metabolism
  • supports vascular responsiveness
  • modulates central nervous function
  • decreases skeletal bone formation
  • breaks down muscle tissue
  • suppresses immune responses
  • affects renal functions.

It’s overall effect is catabolic i.e. breaking down tissues to mobilise resources, especially during times of stress. It s called the stress hormone, because it is released during stress, to help the body deal rapidly and effectively with the stressors.

On a normal day, it is produced in large quantity in the early morning, to provide the energy to get-up-and-go. Production tails off rapidly during the day, so that levels are low when it is time to sleep. This is called a diurnal rhythm. This rhythm is disrupted by exposure to excessive or prolonged periods of stress, causing the adrenal glands to produce too much or too little cortisol.

Cortisol is often measured in serum, where 98% is bound to proteins and thus inactive. Salivary cortisol is free, active and unbound, making the salivary measurement more relevant than the serum measurement. Saliva is sampled 2 or 4 times in a day to assess the diurnal rhythm. When measured together with DHEA,  one can evaluate the effect of stress on the body.


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