What is Cortisol? - Definition, Function & Deficiency Symptoms

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  • 0:01 Cortisol
  • 0:39 Function
  • 2:26 Deficiency
  • 2:54 Excess
  • 3:50 Too Much Stress
  • 4:13 Five Stress Reducers
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Lesson Transcript
Instructor: Laszlo Vass
In this lesson, learn about one of the most important hormones in the body: cortisol. This lesson defines cortisol, how it's made, and its function. Learn about cortisol deficiency, excess cortisol, and the effect it has on homeostasis and regulation in the body.


Have you ever felt stressed out? Most of us have at one point in time. Our body responds to stress in many different ways, but one thing that all stress has in common is that it increases the level of a very powerful hormone called cortisol. Cortisol is a hormone involved in the regulation of metabolism in the cells and helps us regulate stress within the body.

Cortisol is a steroid-based hormone and is synthesized from cholesterol and belongs to a group of hormones called glucocorticoids. Cortisol is made in the adrenal cortex of the adrenal gland, which is near the kidney.


Cortisol, like all steroid-based hormones, is a powerful chemical. Steroid-based hormones have a common mechanism of action in that they enter cells and modify the gene activity in the DNA. The amount of cortisol in your body is driven by the amount of stress you are experiencing. In addition, caffeine consumption, your eating patterns, how much physical activity you get and your sleep patterns all affect how much cortisol is released in your system. As a general rule, your highest level of cortisol occurs just after you get up in the morning and the lowest level is in the evening as you are falling asleep.

Cortisol's main function is to save us when we are under stress. Cortisol does this by provoking the cell to manufacture glucose from proteins and fatty acids. This process is known as gluconeogenesis. What cortisol is doing is saving glucose for the brain and forcing the body to use fatty acids from stored fat as energy.

Cortisol also forces the breakdown of stored proteins into amino acids so that the body can use them for making enzymes or repairing cells. Cortisol increases blood pressure, which increases blood flow and distributes the glucose and other nutrients as quickly as possible to the cells.

Finally, cortisol reduces the inflammatory response as well as the overall immune response in the body. Consequently, stress causes a rise in the amounts of glucose, fatty acids, and amino acids in the blood, all promoted by cortisol. Cortisol is used in treatments like hydrocortisone cream to control inflammatory diseases, such as rashes and allergies. It can also be injected to treat more serious autoimmune conditions, like rheumatoid arthritis.


Hyposecretion, or cortisol deficiency, can result from damage to the adrenal glands. This damage can cause Addison's disease. Persons affected by Addison's disease have low glucose and sodium levels in their blood, increased potassium, and they tend to lose weight. This can also cause low blood pressure and dehydration. Cortisol deficiency is usually treated with corticosteroid replacement therapy to return cortisol to normal levels in the body.


Hypersecretion, or excess of cortisol, occurs in response to stress and as already discussed, results in decreased inflammation and immune response. However, there is a more serious condition called Cushing's Disease that can cause hypersecretion of cortisol. Instead of stress, the cause of Cushing's syndrome is either a tumor of the pituitary gland or adrenal cortex or excess doses of glucocorticoid drugs. It has serious side effects including water and salt retention, high blood pressure, swelling, muscle tissue and bone loss, deposits of excess fat in the abdomen and back of the neck and poor wound healing. Arguably the most severe side effect of Cushing's syndrome is the tendency to develop severe infections before the patient shows any symptoms (this is due to the decreased immune response). Treatment is either surgical removal of the tumor or discontinuing the drugs.

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