What is Cortisol?
Cortisol is a glucocorticoid hormone produced by the adrenal glands in response to signals from the hypothalamic-pituitary-adrenal (HPA) axis. It plays a central role in regulating blood sugar, blood pressure, immune signaling, inflammation, circadian rhythm, and the body’s ability to adapt to physical and psychological stress.
Under normal conditions, cortisol follows a diurnal rhythm—peaking in the early morning to support alertness and metabolic readiness, then gradually declining throughout the day to allow for rest and recovery. Chronic stress, inflammation, sleep disruption, or metabolic strain can alter both cortisol output and rhythm, leading to systemic effects.
Why Test for Cortisol?
Evaluating cortisol levels helps clinicians assess stress physiology, adrenal signaling, and overall neuroendocrine balance. Cortisol testing is commonly used to investigate:
• Chronic stress exposure and reduced stress adaptability
• Fatigue, low energy, or poor resilience
• Sleep disturbances and circadian rhythm disruption
• Blood sugar instability and metabolic strain
• Weight changes, particularly central adiposity
• Inflammatory or immune dysregulation
Cortisol may be measured in serum, saliva, or urine depending on clinical intent and timing considerations.
Clinical Significance of Cortisol Levels
- Low Cortisol Levels: Morning serum cortisol levels below ~6 µg/dL (165 nmol/L) may reflect adrenal insufficiency, HPA axis suppression, impaired pituitary signaling, or reduced stress adaptability following prolonged stress or corticosteroid exposure. Clinically, low cortisol is often associated with morning fatigue, dizziness, low blood pressure, hypoglycemia, exercise intolerance, and poor stress tolerance.
- High Cortisol Levels: Morning serum cortisol levels above ~18–20 µg/dL (500–550 nmol/L) are commonly associated with chronic psychological stress, sleep deprivation, inflammatory conditions, metabolic dysfunction, or prolonged corticosteroid use. Persistently elevated cortisol may contribute to anxiety, sleep disruption, insulin resistance, muscle breakdown, immune suppression, and suppression of thyroid and sex hormone signaling.
Actionable Insights
Cortisol should be interpreted in context rather than as an isolated value. Single serum measurements provide a snapshot, while timed or diurnal assessments offer insight into rhythm and adaptability. A cortisol value within range does not guarantee healthy regulation—flattened diurnal rhythm or elevated evening cortisol may still indicate dysregulation. Cortisol is commonly evaluated alongside glucose markers, thyroid hormones, inflammatory markers, and adrenal and sex hormones to assess system-wide stress response.
When abnormalities are identified, clinical focus often shifts to identifying upstream drivers such as sleep quality, inflammation, metabolic strain, psychological stress, or medication effects. Monitoring trends over time may provide greater insight than one-time measurements.
Optimal Ranges
• Morning Serum Cortisol (8–9 AM): ~6–18 µg/dL
• Evening Cortisol: Should decline significantly from morning levels
Note: Reference ranges vary by laboratory. In functional medicine, some providers may consider a narrower interpretive window to help guide clinical context. These values are not standardized and should be interpreted in conjunction with the ordering provider’s judgment.
"When managing low cortisol, use caution with DHEA or pregnenolone. These precursors may further suppress endogenous cortisol via HPA-axis feedback and worsen adrenal insufficiency. The so-called “pregnenolone steal” is largely unsupported, as there is no shared intra-adrenal pool being diverted. In patients with elevated cortisol, DHEA may also increase downstream cortisol in certain contexts, potentially worsening anxiety, insomnia, or metabolic strain. Prioritize clinical context, serial monitoring, and root-cause evaluation over formulaic supplementation.”
Dr. Mitch Ghen
Disclaimer: Content on the Access Medical Labs blog is for informational purposes only and reflects the views of individual contributors, not necessarily those of Access Medical Labs. We do not endorse specific treatments, products, or protocols. This content is not a substitute for professional medical advice. Always consult a qualified healthcare provider regarding any medical concerns.
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