Cortisols synthesized from cholesterol and its production Is stimulated by pituitary adrenocorticotropic hormone (ACTH) which is regulated by corticotropin releasing factor (CRF). ACTH and CRF secretions are inhibited by high cortisol levels in a negative feedback loop. Cortisol plays a role in the metabolism of proteins, lipids, and carbohydrates .It affects blood glucose levels, helps maintain blood pressure and regulate the immune system.
The level of cortisol in the blood normally rises and falls in a “diurnal variation” pattern. It peaks early in the morning, then declines throughout the day. This pattern can change when a person works irregular shifts and sleeps at different times of the day, and it can become disrupted when a disease or condition either limits or stimulates cortisol production.