Description:

Cortisol is a corticosteroid hormone produced by the adrenal cortex that is involved in the response to stress; it increases blood pressure, blood sugar levels, may cause infertility in women, and suppresses the immune system. In pharmacology, cortisol is referred to as hydrocortisone, and is used to treat allergies and inflammation.

The amount of cortisol present in the serum undergoes diurnal variation, with the highest levels present in the early morning, and the lowest levels present around midnight, 3-5 hours after the onset of sleep. Information about the light/dark cycle is transmitted from the retina to the paired suprachiasmatic nuclei in the hypothalamus. The pattern is not present at birth (estimates of when it starts vary from two weeks to 9 months.)

Changed patterns of serum cortisol levels have been observed in connection with abnormal ACTH levels, clinical depression, psychological stress, and such physiological stressors as hypoglycemia, illness, fever, trauma, surgery, fear, pain, physical exertion or extremes of temperature.

There is also significant individual variation, although a given person tends to have consistent rhythms.Hypercortisolism: Excessive levels of cortisol in the blood result in Cushing's syndrome. Hypocortisolism, or adrenal insufficiency: If on the other hand the adrenal glands do not produce sufficient amounts of cortisol, Addison's disease is the consequence.