Cortisol, often referred to as the stress hormone because of its involvement in the stress response, is produced in the adrenal cortex. It increases blood pressure, blood sugar levels and has an immunosuppressive action. The amount of cortisol present in the blood undergoes diurnal variation, the highest level is present in the early morning, and the lowest level some 3 to 5 hours after sleep onset. Disrupted sleep patterns with constant awakenings, interfere with the release of cortisol.
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.
Those people who work the graveyard shift have been shown to have higher rates of breast cancer, disrupted sleep patterns, and exposure to abnormal hours of artificial light have been shown to interfere with the at least two hormones that affect cancer cell growth.
