Diurnal Variance Testing is a clinical diagnostic procedure that measures the fluctuating levels of specific hormones, neurotransmitters, or metabolites throughout a 24-hour cycle to assess the integrity of the body’s circadian rhythm and endocrine regulation. This type of testing moves beyond single-point measurements, capturing the critical peak and trough patterns that reflect true physiological function, particularly for stress hormones like cortisol and sex hormones. It is essential for diagnosing conditions rooted in circadian disruption, such as adrenal dysfunction or sleep-wake cycle abnormalities.
Origin
The necessity for diurnal testing stems from the chronobiology field, which established that many key physiological processes, especially those governed by the hypothalamic-pituitary-adrenal (HPA) axis, follow a predictable, time-dependent pattern. A single morning blood draw often fails to capture the dynamic regulatory capacity of the endocrine system. The term highlights the importance of measuring this inherent daily variance for accurate clinical assessment.
Mechanism
The test operates by collecting biological samples, such as saliva or urine, at multiple predefined time points across the day and night. This allows clinicians to map the individual’s unique hormonal curve, comparing the amplitude and timing of the rhythm to established healthy ranges. Deviations from the expected diurnal curve—for example, a flattened cortisol slope—indicate compromised HPA axis feedback and impaired adaptation to stress, guiding precise chronotherapeutic interventions.
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