This is a test used to help diagnose Cushing's syndrome or Addison's disease.
Cortisol is a hormone produced by the small organs on top of each kidney (adrenal glands). Production and secretion of cortisol is stimulated by ACTH (adrenocorticotropic hormone), a hormone produced by the pituitary gland - a tiny organ located inside the head below the brain. Cortisol has a range of roles in the body. It helps break down protein, glucose, and lipids, maintain blood pressure, and regulate the immune system. Heat, cold, infection, trauma, stress, exercise, obesity, and debilitating disease can influence cortisol concentrations. The hormone is secreted in a daily pattern, rising in the early morning, peaking around 8 a.m., and declining in the evening. This pattern, which is sometimes called the "diurnal variation" or "circadian rhythm," changes if you work irregular shifts (such as the night shift) and sleep at different times of the day.
Inadequate amounts of cortisol can cause nonspecific symptoms such as weight loss, muscle weakness, fatigue, low blood pressure, and abdominal pain. Sometimes decreased production combined with a stressor can cause an adrenal crisis that requires immediate medical attention.
Too much cortisol can cause increased blood pressure, high blood sugar, obesity, fragile skin, purple streaks on the abdomen, muscle weakness, and osteoporosis. Women may have irregular menstrual periods and increased facial hair; children may have delayed development and a short stature.
PREPARATION FOR TEST
Typically, blood will be drawn from a vein in the arm, but sometimes urine or saliva may be tested. Cortisol blood tests may be drawn at about 8 am, when cortisol should be at its peak, and again at about 4 pm, when the level should have dropped. Sometimes a resting sample will be obtained late in the evening to look at cortisol when it should be at its lowest concentration in the blood (about midnight). Obtaining more than one sample allows the caregiver to evaluate the daily pattern of cortisol secretion.
Cortisol testing of saliva can be performed. Although the sampling is less stressful than a blood draw, it requires special care and the test is not yet widely available. Saliva testing is a snapshot of the cortisol present at the time it is collected.
Cortisol testing may also be done with a 24-hour urine collection. You should avoid drinking alcoholic beverages before and during the urine collection.
8 am: 5-23 mcg/dL or 138-635 nmol/L (SI units)
4 pm: 3-13 mcg/dL or 83-359 nmol/L (SI units)
Child 1-16 years
8 am: 3-21 mcg/dL
4 pm: 3-10 mcg/dL
Newborn: 1-24 mcg/dL
Ranges for normal findings may vary among different laboratories and hospitals. You should always check with your doctor after having lab work or other tests done to discuss the meaning of your test results and whether your values are considered within normal limits.
MEANING OF TEST
Your caregiver will go over the test results with you and discuss the importance and meaning of your results, as well as treatment options and the need for additional tests if necessary.
OBTAINING THE TEST RESULTS
It is your responsibility to obtain your test results. Ask the lab or department performing the test when and how you will get your results.