AM serum cortisol
Single blood draw at 8-10 AM. Captures the cortisol awakening response peak. Reference range typically 5-25 µg/dL. Use for:
- Adrenal insufficiency screening
- Cushing's screening (with dexamethasone suppression)
- General assessment of HPA function
- Pituitary disease evaluation
Salivary cortisol curve
4 saliva samples across the day:
- Upon waking
- +30 minutes after waking
- Midday
- Evening (before bed)
Captures the cortisol awakening response (CAR) plus diurnal pattern.
Comparison
| Test | Captures | Misses |
|---|---|---|
| AM serum | Peak level | Diurnal pattern |
| Salivary curve | Full rhythm | Quantitative reference points |
| 24h urinary | Total daily output | Pattern |
Pattern interpretation
- Normal curve, high morning, declining through day, low evening
- Flattened curve, chronic HPA dysregulation, often burnout
- Blunted morning rise, reduced CAR; chronic stress
- Elevated evening cortisol, chronic stress; sleep disruption
- Elevated total cortisol, early-stage chronic stress; sometimes Cushing's
- Suppressed all values, late-stage HPA dysregulation
When to use each
AM serum sufficient for:
- Initial endocrine evaluation
- Suspected Cushing's or adrenal insufficiency
- General hormone panel inclusion
Salivary curve adds value for:
- Chronic stress symptoms
- Burnout evaluation
- Sleep disruption with morning fatigue
- Tracking response to stress reduction
The clinical pearl: AM serum cortisol is sufficient for most evaluation. Salivary curve adds resolution for patients with chronic stress symptoms where the rhythm matters more than the peak.
Bottom line
AM serum cortisol captures the peak. Salivary curve captures the rhythm. Each has appropriate use cases. For burnout and chronic stress evaluation, the curve is more informative.
8-10 AM
standard serum draw timing
4 samples
salivary curve typical
Pattern
often more informative than peak