Afternoon Cortisol Level of 14.7 μg/dL: Clinical Interpretation
An afternoon cortisol level of 14.7 μg/dL is within the normal physiological range and does not indicate adrenal dysfunction. This value reflects appropriate hypothalamic-pituitary-adrenal axis function and requires no further evaluation in an asymptomatic patient 1.
Normal Afternoon Cortisol Values
- Afternoon cortisol levels naturally decline from morning peaks due to the circadian rhythm of cortisol secretion, with afternoon values typically ranging from approximately 5-15 μg/dL 2, 3.
- Your level of 14.7 μg/dL falls at the upper end of the normal afternoon range, which is physiologically appropriate and does not suggest hypercortisolism 1.
- Morning cortisol levels >14 μg/dL effectively rule out adrenal insufficiency according to the Journal of Internal Medicine guidelines, and your afternoon value exceeds this threshold 1.
Why Afternoon Timing Matters
- Cortisol follows a predictable circadian rhythm with peak levels occurring at 8:00-9:00 AM (typically 10-25 μg/dL) and nadir levels occurring around midnight 4, 3.
- Afternoon measurements are inherently less reliable for diagnostic purposes because they capture cortisol during its declining phase, making interpretation more challenging than morning values 4, 2.
- Single afternoon measurements can miss important fluctuations that occur during the 24-hour circadian cycle, potentially leading to misinterpretation if not considered in proper context 2.
When Additional Testing Would Be Warranted
If you have symptoms suggestive of cortisol excess (weight gain, central obesity, purple striae, easy bruising, proximal muscle weakness, hypertension), further evaluation is needed despite this normal afternoon value 1:
- First-line screening: Overnight 1-mg dexamethasone suppression test (1 mg at 11 PM, measure cortisol at 8 AM; normal <50 nmol/L or <1.8 μg/dL) 4.
- Late-night salivary cortisol (collected at bedtime on 2-3 occasions) is highly specific for detecting loss of normal circadian rhythm seen in Cushing's syndrome 4.
- 24-hour urinary free cortisol serves as an ancillary test when other results are equivocal 4.
If you have symptoms of adrenal insufficiency (fatigue, weight loss, nausea, hyperpigmentation, hypotension), obtain a morning cortisol at 8:00-9:00 AM 1, 4:
- Morning cortisol >14 μg/dL rules out adrenal insufficiency 1.
- Morning cortisol <5 μg/dL confirms adrenal insufficiency 5.
- Values between 5-14 μg/dL require ACTH stimulation testing for definitive diagnosis 5.
Important Factors That Can Affect Interpretation
- Medications: CYP3A4 inducers (anticonvulsants, rifampin) increase cortisol clearance and may lower measured levels; oral estrogens and pregnancy increase cortisol-binding globulin and elevate total cortisol 6, 1, 4.
- Stress and illness: Acute physical or psychological stress can temporarily elevate cortisol levels at any time of day 1, 7.
- Disrupted sleep patterns: Shift workers and those with irregular sleep schedules have altered cortisol rhythms that make single measurements unreliable 4.
Bottom Line
Your afternoon cortisol of 14.7 μg/dL requires no action in the absence of clinical symptoms. If symptoms of either cortisol excess or deficiency are present, proceed with appropriate morning testing or screening tests as outlined above rather than repeating afternoon measurements 1, 4.