Cortisol in blood
Test Description:
In response to a stimulus such as stress, the hypothalamus secretes corticotropinreleasing
hormone. This hormone stimulates the secretion of adrenocorticotropic
hormone (ACTH) by the anterior pituitary gland. ACTH, in turn, causes the adrenal
cortex to release the glucocorticoid hormone, cortisol. Cortisol has several functions,
including:
• stimulation of glucose formation (gluconeogenesis)
• stimulation of stored energy molecular breakdown (fats, proteins, carbohydrates)
• promotion of sympathetic responses to stressors
• reduction of inflammation and immune function
• stimulation of gastric acid secretion
Cortisol levels in the blood provide valuable information regarding the functioning
of the adrenal cortex. Cortisol is normally secreted in a diurnal pattern, with
the peak or highest levels being between 6 and 8 a.m. and trough, or lowest, levels
being at midnight.
Normal Values
8 a.m.–12 noon 5.0–25.0 mcg/dL (138–690 nmol/L SI units)
12 noon–8 p.m. 5.0–15.0 mcg/dL (138–410 nmol/L SI units)
8 p.m.–8 a.m. 0.0–10.0 mcg/dL (0–276 nmol/L SI units)
Possible Meanings of Abnormal Values
Increased Decreased
Adrenal adenoma Addison’s disease
Burns Adrenal insufficiency
Cushing’s disease Hypoglycemia
Cushing’s syndrome Hypopituitarism
Eclampsia Hypothyroidism
Ectopic ACTH-producing tumors Liver disease
Exercise Postpartum pituitary necrosis
Hyperpituitarism
Hypertension
Hyperthyroidism
Infectious disease
Obesity
Pancreatitis (acute)
Pregnancy
Shock
Stress
Surgery
Contributing Factors to Abnormal Values
• Levels of cortisol may vary with exercise, sleep, and stress.
• Hemolysis of the sample may alter test results.
• Drugs which may increase cortisol levels include: amphetamines, estrogens, ethyl
alcohol, lithium carbonate, methadone, nicotine, oral contraceptives, spironolactone,
synthetic glucocorticoids (prednisone, prednisolone).
• Drugs which may decrease cortisol levels include: androgens, barbiturates, dexamethasone,
levodopa, phenytoin.
Interventions/Implications
Pretest
• Explain to the patient the purpose of the test and the need for a blood sample to be drawn.
• Fasting and limited physical activity for 10 to 12 hours is required prior to the test.
Procedure
• A 7-mL blood sample is drawn in a red-top collection tube at 8 AM and again at 4 p.m.
• Gloves are worn throughout the procedure.
Posttest
• Apply pressure at venipuncture site. Apply dressing, periodically assessing for continued
bleeding.
• Label the specimen and transport it to the laboratory. Include the time when the sample
was obtained and any medications which might affect the test results.
• Report abnormal findings to the primary care provider.
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