What is Cortisol and How Does it Affect My Body?

Cortisol, also called Hydrocortisone, is a hormone known as a glucocorticoid that affects the metabolism of carbohydrates, proteins, fats, and especially glucose. It increases blood sugar levels by stimulating the release of glucose from glucose stores in your body’s cells. It also acts to inhibit insulin, which affects glucose transport into cells.
The hypothalamus, the pituitary gland, and the adrenal glands all work together to create cortisol. First, the hypothalamus releases corticotropin-releasing hormone (CRH), which stimulates the pituitary gland to produce adrenocorticotropic hormone (ACTH). The production of ACTH in turn stimulates a part of the adrenal glands known as the adrenal cortex to produce cortisol. Once cortisol is released into the blood stream, it binds to certain proteins. When those proteins are all taken, the excess cortisol (called free cortisol) flows freely in the blood triggering your body to stop producing it. Cortisol levels normally rise and fall during the day. The levels are usually higher in the morning and lower in the evening reaching its lowest point around midnight. For those who sleep during the day and are active at night, these levels are reversed: lower in the morning and higher in the evening.
Increased levels of cortisol can indicate a variety of conditions including Cushing's syndrome, hyperthyroidism, obesity, ACTH-producing tumors, and high levels of stress. Higher levels may also be caused by pregnancy and some drugs such as estrogen, oral contraceptives, amphetamines, cortisone, and spironolactone. Decreased levels of cortisol can be found in Addison's disease, hypothyroidism, and hypopituitarism. Low levels can also be caused by some drugs such as androgens, aminoglutethimide, betamethasone, some other steroid medications, danazol, lithium, levodopa, metyrapone and phenytoin (Dilantin). Cortisol levels that remain the same through out the day can be an early sign adrenal malfunction.
If your doctor decides to test your cortisol levels, there are three different methods that he/she may choose from. The first is a blood test.
Since cortisol levels vary throughout the day the test must be done twice in the same day, usually around 8am and again around 4pm. These times must be adjusted though for people who sleep during the day and are awake at night so be sure to inform your doctor of your sleep habits. Normal levels for adults range in the morning from 6–28 mg and in the afternoon from 2–12 mg.
Another method your doctor may choose is the saliva test. Salivary cortisol is stable at room temperature for days, is non-invasive and can be done at home by the patient. This test is useful in patients with suspected intermittent Cushing’s disease who need to collect numerous samples over a long period of time.
The 24-hour urine free cortisol test is the most accurate and specific method for obtaining a cortisol index. When the amount of cortisol exceeds the capacity of its carrier proteins to bind, free cortisol levels in the blood rise rapidly, increasing the amount that is filtered into the urine. If your doctor chooses this method, he or she will ask you collect all of your urine during a 24-hour period and will provide you with a container in which to do so. He or she will also instruct you as to exactly when to begin and how you need to do it. Normal cortisol levels for an adult during a 24-hour period range from 10 to 100 mg. Which method your doctor chooses will depend on what the suspected problem may be.

This information is not a substitute for medical advice and is not intended as a diagnosis. Any questions regarding your health should be directed to your doctor.

References
Cortisol Tests. (n.d.). Encyclopedia of Medicine. Retrieved April 12, 2007, from Answers.com Web site: http://www.answers.com/topic/cortisol-tests

Bishop, Fody, & Schoeff, 2005. Clinical Chemistry Fifth Ed. Lippincott, Williams & Wilkins