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Cortisol Test

Cortisol is a hormone that plays a role in the metabolism of proteins, lipids, and carbohydrates.

It affects blood glucose levels, helps maintain blood pressure, and helps regulate the immune system.

Most cortisol in the blood is bound to a protein; only a small percentage is “free” and biologically active.

Free cortisol is secreted into the urine and is present in the saliva.

This test measures the amount of cortisol in the blood, urine, or saliva.

A cortisol test may be used to help diagnose Cushing syndrome, a condition associated with excess cortisol, or to help diagnose adrenal insufficiency or Addison disease, conditions associated with deficient cortisol.

Normally, the level of cortisol in the blood rises and falls in a “diurnal variation” pattern, peaking early in the morning, then declining throughout the day and reaching its lowest level about midnight.

Cortisol is produced and secreted by the adrenal glands. Production of the hormone is regulated by the hypothalamus in the brain and by the pituitary gland, a tiny organ located below the brain.

When the blood cortisol level falls, the hypothalamus releases corticotropin-releasing hormone (CRH), which directs the pituitary gland to produce ACTH(adrenocorticotropic hormone). ACTH stimulates the adrenal glands to produce and release cortisol.

Blood cortisol testing evaluates both protein-bound and free cortisol while urine and saliva testing evaluate only free cortisol, which should correlate with the levels of free cortisol in the blood.

Multiple blood and/or saliva cortisol levels collected at different times, such as at 8 am and 4 pm, can be used to evaluate both cortisol levels and diurnal variation.

A 24-hour urine cortisol sample will not show diurnal variation; it will measure the total amount of unbound cortisol excreted in 24 hours.

A cortisol test may be ordered when a person has symptoms that suggest a high level of cortisol and Cushing syndrome, such as

· High blood pressure (hypertension)

· High blood sugar (glucose)

· Obesity, especially in the trunk

· Fragile skin

· Purple streaks on the abdomen

· Muscle wasting and weakness

· Osteoporosis

Testing may be ordered when women have irregular menstrual periods and increased facial hair; children may have delayed development and a short stature.

This test may be ordered when someone has symptoms suggestive of a low level of cortisol, adrenal insufficiency orAddison disease, such as:

· Weight loss

· Muscle weakness

· Fatigue

· Low blood pressure

· Abdominal pain

· Dark patches of skin (this occurs in Addison disease but not secondary adrenal insufficiency)

Sometimes decreased production combined with a stressor can cause an adrenal crisis that can be life-threatening and requires immediate medical attention.

Symptoms of a crisis may include:

· Sudden onset of severe pain in the lower back, abdomen, or legs

· Vomiting and diarrhea, resulting in dehydration

· Low blood pressure (hypotension)

· Loss of consciousness

Suppression or stimulation testing is ordered when initial findings are abnormal.

Cortisol testing may be ordered at intervals after a diagnosis of Cushing syndrome or Addison disease to monitor the effectiveness of treatment.

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 significantly.

Sometimes a resting sample will be obtained to measure cortisol when it should be at its lowest level (just before sleep); this is often done by measuring cortisol in saliva rather than blood to make it easier to obtain the sample. Saliva for cortisol testing is usually collected by inserting a swab into the mouth and waiting a few minutes while the swab becomes saturated with saliva.

Obtaining more than one sample allows the health practitioner to evaluate the daily pattern of cortisol secretion

Sometimes urine is tested for cortisol; this usually requires collecting all of the urine produced during a day and night (a 24-hour urine) but sometimes may be done on a single sample of urine collected in the morning.

NORMAL RANGE:

The normal range varies throughout the day, with normal cortisol levels higher in the morning and lower in the afternoon and evening.

Morning: 5-23 mcg/dL

Evening: 3-16 mcg/dL

HIGH RESULTS INDICATE:

High results may indicate Cushing’s syndrome, severe liver or kidney disease, depression or high levels of chronic stress, hyperthyroidism, obesity, or a recent surgery, illness or whole body infection.

LOW RESULTS INDICATE:

Low results may indicate Addison’s disease due to a head injury or autoimmune disorder, shock from an injury or trauma, or Sheehan’s syndrome (a lack of cortisol due to damage to the pituitary gland during childbirth).