Cortisol levels can vary according to the time of day the testing is performed. For children, normal levels range from 3 to 21 micrograms per decilitre (mcg/dl) for a blood test or 83 to 580 nanomoles per litre (nmol/L) in a urine sample. The cortisol test is recommended by a physician to test for medical conditions or abnormalities associated with the pituitary and adrenal glands.
Cortisol is classified as a steroid hormone that is produced by the adrenal cortex. It is released in response to adrenocorticotropic hormone (ACTH). When cortisol levels are tested, the measurements are markers of how the pituitary and adrenal glands are functioning. Cortisol helps with metabolism (energy) and aiding in the management of stress.
Cortisol testing is performed in the morning and afternoon by either a blood-serum test or urine analysis. A morning test for a child can range from 3 to 21mcg/dl and afternoon testing ranges are 3 to 10mcg/dl for a blood-serum test. The normal range for a urine test in children is 83 to 380 nmol/L in the morning and 83 to 276 nmol/L in the afternoon. A newborn's blood level range in cortisol is 1 to 24mcg/dl or 27 to 663 nmol/L for a urine test.
An abnormal level of cortisol can be a sign of medical conditions and/or diseases. A high level can be a sign of Cushing's syndrome, caused by an overactive adrenal gland. It can also be an indicator of liver or kidney disease, hyperthyroidism (overactive thyroid), depression and obesity. Low levels of cortisol can indicate Addison's disease, low levels of cortisol caused by damage to the adrenal glands. Low cortisol levels can also be an indication of internal bleeding, head injury, infection and autoimmune diseases.
Cortisol levels vary during the day with the peak time in a 24-hour cycle occurring at approximately 7 to 8 a.m., and lowest levels are observed at midnight, called the resting level. Generally, to ensure adequate testing levels, cortisol can also be tested again at 4 p.m., when the levels have normally dropped.
Taking certain medications, consuming certain foods, medical procedures and medical conditions can have an effect on the levels of cortisol when testing. A health-care professional will perform a full physical examination and medical history to rule out any abnormalities in a cortisol test. Medical conditions, such as stress, both physical and emotional; pregnancy; and hypoglycaemia (low blood sugar) can alter the cortisol test results. Medications that have the potential to affect the cortisol test include birth-control pills, amphetamines, corticoseteroids and oestrogen.