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Diurnal Cortisol Profile – Meaning and Diagnosis

The diurnal cortisol profile measures how cortisol levels in blood or saliva change throughout the day. It helps diagnose hormonal disorders such as Cushing syndrome or adrenal insufficiency.

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Things worth knowing about "Diurnal Cortisol Profile"

The diurnal cortisol profile measures how cortisol levels in blood or saliva change throughout the day. It helps diagnose hormonal disorders such as Cushing syndrome or adrenal insufficiency.

What Is the Diurnal Cortisol Profile?

The diurnal cortisol profile is a diagnostic tool that measures cortisol levels at several defined time points throughout the day. Cortisol is a vital stress hormone produced by the adrenal cortex that regulates many body functions, including metabolism, immune response, and the reaction to stress.

Cortisol naturally follows a circadian rhythm: levels are highest in the morning shortly after waking and gradually decline throughout the day, reaching their lowest point at night. The diurnal cortisol profile maps this pattern and helps identify deviations from the norm.

When Is a Diurnal Cortisol Profile Ordered?

A physician may order a diurnal cortisol profile when a disorder of the adrenal cortex or hormonal regulation is suspected. Common indications include:

Suspected Cushing syndrome (hypercortisolism – excess cortisol)
Suspected adrenal insufficiency (Addison disease – insufficient cortisol)
Unexplained fatigue or chronic exhaustion
Sleep disturbances or disrupted sleep-wake cycles
Monitoring of existing hormone therapy
Investigation of unexplained weight gain, high blood pressure, or osteoporosis

How Is the Diurnal Cortisol Profile Performed?

Blood Measurement

In the traditional approach, blood samples are taken at defined time points – typically in the morning (around 8 a.m.), at midday, and in the evening (around 8–11 p.m.). Laboratory analysis then determines the cortisol concentration. Because a blood draw itself can cause brief stress and temporarily elevate cortisol, the first sample is often collected after a short rest period.

Saliva Measurement

An increasingly popular and patient-friendly method is salivary cortisol measurement. The patient collects saliva samples at fixed times – typically upon waking, at midday, in the evening, and before bed – using a small absorbent swab (salivette). This method is stress-free, can be performed at home, and reliably reflects the biologically active fraction of cortisol.

Urine Measurement

As a complementary approach, the free cortisol in a 24-hour urine collection can be measured. This captures the total cortisol output over a full day and is particularly useful for confirming Cushing syndrome.

Interpreting the Results

In a healthy individual, the cortisol profile typically shows:

Morning (approx. 8 a.m.): Highest level (approx. 170–500 nmol/l in serum)
Midday: Clearly declining values
Evening/Night: Lowest level (below 50 nmol/l in serum)

Deviations from this pattern may indicate various conditions:

Persistently elevated values or failure to decline in the evening: May suggest Cushing syndrome, chronic stress, or depression
Persistently low values: May point to adrenal insufficiency (Addison disease) or hypopituitarism
Flattened profile without a clear morning peak: Can be associated with sleep disorders, burnout, or chronic fatigue syndrome

Preparation and Important Notes

To ensure meaningful results, patients should observe the following:

Avoid intense physical activity and significant stress before sample collection
Inform the physician about any corticosteroid medications, as these can interfere with results
Avoid alcohol and large amounts of caffeine on the day of testing if possible
Adhere strictly to the prescribed collection times, as timing is critical for accurate interpretation

References

Nieman LK et al.: The Diagnosis of Cushing's Syndrome: An Endocrine Society Clinical Practice Guideline. Journal of Clinical Endocrinology and Metabolism, 2008; 93(5): 1526–1540.
Clow A et al.: The Cortisol Awakening Response: More than a Measure of HPA Axis Function. Neuroscience and Biobehavioral Reviews, 2010; 35(1): 97–103.
World Health Organization (WHO): Endocrine Disorders – Adrenal Gland Function. WHO Technical Report, Geneva.

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