EBM Consult

Cortisol (Serum) Level

    Lab Test
    • Cortisol (Serum)
    • Measure of serum cortisol.  It is performed on patients who are suspected to have hyper functioning or hypo functioning adrenal glands.
    Reference Range
    • Adults:
      • 8 AM to noon:  5-25 mcg/dL (138-690 nmol/L)
      • 8 PM to 8 AM:  0-10 mcg/dL (0-276 nmol/L)* (PDR)
    • Adult/elderly:
      • 8 AM:  5-23 mcg/dL (138-635 nmol/L)
      • 4 PM:  3-13 mcg/dL (83-359 nmol/L)
    • Child: 1-16 years:
      • 8 AM:  3-21 mcg/dL
      • 4 PM:  3-10 mcg/dL
    • Newborn:  1-24 mcg/dL
    Indications & Uses
    • Suspected adrenal insufficiency, e.g., Addison's Disease - an unstimulated serum cortisol value < 80 nmol/L, in the absence of corticosteroid-binding globulin deficiency, soundly implies adrenal insufficiency
    • Suspected Cushing's syndrome - an elevated cortisol level is consistent with a diagnosis of Cashing's syndrome.  Midnight is the optimal tine for obtaining a cortisol level.
    Clinical Application
    • A typical feedback loop/mechanism exists for cortisol which is known to coordinate the function of the hypothalamus, pituitary gland, and adrenal gland.  Corticotropin-releasing hormone (CRH) is made in the hypothalamus, which stimulates adrenocorticotropic hormone (ACTH) production in the anterior pituitary gland.  ACTH then stimulates the adrenal cortex to produce cortisol.  The rising levels of cortisol act as a negative feedback to curtail further production of CRH and ACTH. Cortisol is a potent glucocorticoid released from the adrenal cortex and affects the metabolism of carbohydrates, proteins, and fats.  It also has a significant impact on glucose serum levels. 
    • Cortisol levels normally rise and fall during the day; this is called the diurnal variation.  Cortisol levels are highest around 6 AM to 8 AM and gradually fall during the day, reaching their lowest point around midnight. If blood is collected at 8 AM and again at 4 PM, the 4 PM value is anticipated to be one third to two thirds of the 8 AM value. Because tests for serum cortisol measure both free (bioactive) and protein-bound (non active) cortisol, additional testing for only free cortisol in urine may be useful.
    • Increased levels may indicate:
      • Cushing disease, ectopic ACTH-producing tumors, stress, Cushing syndrome (adrenal adenoma or carcinoma), hyperthyroidism, obesity
    • Decreased levels may indicate:
      • Adrenal hyperplasia, Addison disease, hypopituitarism, hypothyroidism
    Related Tests
    • Adrenocorticotropic hormone (ACTH) stimulation - this test is used for the differential diagnosis of Cushing syndrome or Addison disease
    • Adrenocorticotropic (ACTH) hormone - a test of anterior pituitary gland function that affords the greatest insight into the causes of either Cushing syndrome or Addison disease
    • Dexamethasone suppression - important for diagnosing Cushing syndrome and distinguishing its cause
    • Cortisol, urine - performed on patients who are suspected to have hyper functioning or hypo functioning adrenal glands
    Drug-Lab Interactions
    • Results increased in:  depression, hyperthyroidism, hypoglycemia, obesity pregnancy, stress (physical and emotional)
    • Results decreased in:  cirrhosis, hepatitis, hypothyroidism
    • Drugs that may cause increased levels include:  amphetamines, cortisone, estrogen, oral contraceptives, and spironolactone (Aldactone)
    • Drugs that may cause decreased levels include:  androgens, aminoglutethimide, betamethasone and other exogenous steroid medications, danazol, lithium, levodopa, metyrapone, and phenytoin (Dilantin)
    Test Tube Needed
    • Heparinized tube* (PDR)
    • Red or green top tube
    • Assess the patient for signs of physical stress (e.g., infection, acute illness) or emotional stress and report these to the physician. 
    • Collect a venous blood sample in the morning after the patient has had a good night's sleep. 
    • Collect another blood sample at about 4 PM. 
    • Indicate the time of the venipuncture on the laboratory slip. 
    • Apply pressure or a pressure dressing to the venipuncture site and observe the site for bleeding.
    Storage and Handling
    • Store at 4°C for up to two days.
    • Freeze sample for storage beyond two days.
    What To Tell Patient Before & After
    • Explain the procedure to the patient to minimize anxiety.
    • LaGow B et al., eds. PDR Lab Advisor. A Comprehensive Point-of-Care Guide for Over 600 Lab Tests.  First ed. Montvale, NJ: Thomson PDR; 2007.
    • Pagana K, Pagana TJ eds. Mosby's Manual of Diagnostic and Laboratory Tests. 5th Ed.  St. Louis, Missouri. 2014.

MESH Terms & Keywords

  • Cortisol