Cortisol Measurement – Levels, Methods and Significance
Cortisol measurement is a laboratory test used to determine cortisol levels in blood, urine, or saliva. It helps diagnose hormonal disorders such as Cushing syndrome or Addison disease.
Things worth knowing about "Cortisol Measurement"
Cortisol measurement is a laboratory test used to determine cortisol levels in blood, urine, or saliva. It helps diagnose hormonal disorders such as Cushing syndrome or Addison disease.
What Is Cortisol Measurement?
Cortisol measurement is a diagnostic procedure used to assess the level of the stress hormone cortisol in the body. Cortisol is a vital hormone produced by the adrenal cortex that regulates many essential body functions, including metabolism, immune response, blood pressure, and the stress response. The test is typically performed using blood, urine, or saliva samples and provides important information about the function of the adrenal glands and the pituitary gland.
How Is Cortisol Measured?
Several testing methods are available depending on the clinical question:
- Blood test (serum cortisol): The most common method. Because cortisol levels fluctuate significantly throughout the day (circadian rhythm), blood is usually drawn in the morning between 7 and 9 a.m. and again in the evening. Morning levels are physiologically the highest.
- 24-hour urine collection (free cortisol): All urine produced over a 24-hour period is collected and analyzed for free cortisol content. This method provides an overview of overall daily cortisol production.
- Saliva test (salivary cortisol): The late-night salivary cortisol level (around 11 p.m.) is particularly diagnostically useful, as it is very low in healthy individuals. An elevated late-night value may indicate Cushing syndrome.
- Dexamethasone suppression test: A synthetic corticosteroid (dexamethasone) is administered to suppress cortisol production. If cortisol levels remain elevated despite this, autonomous cortisol overproduction may be present.
When Is Cortisol Measurement Used?
Cortisol testing is ordered in a variety of clinical situations, including:
- Suspected Cushing syndrome (cortisol overproduction)
- Suspected Addison disease or adrenal insufficiency (too little cortisol)
- Investigation of chronic fatigue, unexplained weight changes, or mood disturbances
- Monitoring of corticosteroid therapy
- Evaluation of adrenal or pituitary tumors
- Assessment of stress-related symptoms, sleep disorders, or prolonged psychological burden
What Are Normal Cortisol Levels?
Reference ranges may vary slightly between laboratories and testing methods. General guideline values are:
- Morning (8 a.m.): approx. 170–540 nmol/L (6–20 µg/dL)
- Evening (8 p.m.): approx. 64–340 nmol/L (2–12 µg/dL)
- 24-hour urine (free cortisol): approx. 30–145 µg/24 h
- Late-night saliva: below 1.8 nmol/L (below 0.65 µg/dL)
Deviations from these values may indicate disease of the adrenal glands or pituitary, but must always be interpreted within the clinical context.
Elevated Cortisol: Possible Causes
Persistently elevated cortisol levels can have several causes:
- Cushing syndrome: Overproduction of cortisol due to a pituitary or adrenal tumor
- Chronic stress: Ongoing psychological or physical strain
- Corticosteroid medication: Such as prednisolone or dexamethasone
- Pregnancy, depression, or obesity can also influence cortisol levels
Low Cortisol: Possible Causes
An abnormally low cortisol level may indicate:
- Addison disease (primary adrenal insufficiency): The adrenal glands produce insufficient cortisol, often due to an autoimmune process
- Secondary adrenal insufficiency: Insufficient stimulation of the adrenal glands by the pituitary gland (insufficient ACTH production)
- Abrupt discontinuation of long-term corticosteroid therapy
Preparation and Procedure
To ensure reliable cortisol measurement results, the following should be observed:
- Blood draws should ideally be performed in the morning between 7 and 9 a.m. (fasting or after a light meal, depending on laboratory instructions).
- Intense physical or emotional stress immediately before testing can distort results.
- Certain medications (e.g., corticosteroids, oral contraceptives) can affect cortisol levels and should be disclosed to the treating physician.
- For 24-hour urine collection, a complete and accurate collection is essential for valid results.
Clinical Significance
Cortisol measurement is a central tool in endocrinological diagnostics. It not only enables the diagnosis of serious conditions such as Cushing syndrome and Addison disease, but also provides valuable insight into the overall stress burden on the body. Chronically elevated cortisol levels over time are associated with increased risk of cardiovascular disease, diabetes, osteoporosis, and mental health disorders. Early diagnosis and appropriate treatment are therefore of great importance.
References
- Nieman, L.K. et al. - The Diagnosis of Cushing's Syndrome: An Endocrine Society Clinical Practice Guideline. Journal of Clinical Endocrinology and Metabolism, 2008.
- Bornstein, S.R. et al. - Diagnosis and Treatment of Primary Adrenal Insufficiency: An Endocrine Society Clinical Practice Guideline. Journal of Clinical Endocrinology and Metabolism, 2016.
- World Health Organization (WHO) - Endocrine System Disorders: Overview and Diagnostic Standards, WHO Technical Guidelines.
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