Do the cosyntropin (ACTH) stimulation test results (baseline cortisol 14.9 µg/dL, 30‑minute cortisol 29.9 µg/dL, 60‑minute cortisol 33.9 µg/dL) and ACTH level 28.9 pg/mL indicate adrenal insufficiency?

Adrenal Insufficiency is NOT Present Based on These Results

These cosyntropin stimulation test results are normal and do not indicate adrenal insufficiency. The peak cortisol of 33.9 µg/dL at 60 minutes exceeds all diagnostic thresholds, and the ACTH level of 28.9 pg/mL is within normal range, ruling out both primary and secondary adrenal insufficiency.

Interpretation of Your Results

Cortisol Response Analysis

Your stimulated cortisol values show:

• Baseline: 14.9 µg/dL
• 30 minutes: 29.9 µg/dL
• 60 minutes: 33.9 µg/dL (peak)

The FDA-approved diagnostic threshold states that stimulated cortisol <18 µg/dL at 30 or 60 minutes is suggestive of adrenocortical insufficiency 1. Your peak value of 33.9 µg/dL is nearly double this cutoff, indicating robust adrenal function.

The Endocrine Society guidelines establish that a peak cortisol >18 µg/dL (500 nmol/L) after cosyntropin stimulation excludes adrenal insufficiency 2. Your result far exceeds this threshold at both 30 and 60 minutes.

ACTH Level Assessment

Your ACTH of 28.9 pg/mL is within the normal reference range (typically 10-60 pg/mL). This is critical because:

• Primary adrenal insufficiency requires ACTH >2-fold the upper limit of normal (typically >66 pmol/L or ~300 pg/mL) combined with low cortisol 2
• Your normal ACTH with robust cortisol response definitively excludes primary adrenal insufficiency
• The appropriate cortisol response also excludes secondary (central) adrenal insufficiency

Why Both Time Points Matter

While both your 30-minute (29.9 µg/dL) and 60-minute (33.9 µg/dL) values are diagnostic, the 30-minute value has been specifically validated against the insulin tolerance test (the historical gold standard) 2. However, cortisol levels are typically slightly higher at 60 minutes in normal responders 2, which your results demonstrate perfectly with the continued rise from 29.9 to 33.9 µg/dL.

Important Caveats About Assay Variability

Critical consideration: The interpretation assumes your laboratory uses a modern immunoassay or mass spectrometry. Recent evidence shows:

• Newer monoclonal antibody assays may have different cutoff values ranging from 14.6-17.0 µg/dL depending on the specific platform 3, 4, 5
• Your peak of 33.9 µg/dL exceeds even the most conservative thresholds across all assay types
• The traditional 18 µg/dL cutoff was established with older polyclonal antibody assays 6, 2

Even with assay-specific variations, your robust response leaves no diagnostic ambiguity.

Factors That Could Falsely Alter Results

Your results should be interpreted cautiously if you were taking:

• Estrogen-containing medications (oral contraceptives, hormone replacement): These elevate cortisol-binding globulin, artificially raising total cortisol levels 6, 1
• Glucocorticoids or spironolactone: Should be stopped on the day of testing 1
• Strong CYP3A4 inhibitors: Can affect cortisol metabolism 6

If you have conditions affecting protein binding (cirrhosis, nephrotic syndrome, critical illness), total cortisol measurements may be inaccurate 6, 1.

Clinical Bottom Line

No further testing or treatment for adrenal insufficiency is warranted. Your hypothalamic-pituitary-adrenal axis is functioning normally. If you have symptoms that prompted this evaluation (fatigue, hypotension, hyponatremia), alternative diagnoses should be pursued 2.

The combination of:

1. Normal baseline ACTH (28.9 pg/mL)
2. Robust cortisol response (peak 33.9 µg/dL)
3. Appropriate incremental rise (baseline 14.9 → peak 33.9 µg/dL, delta of 19 µg/dL)

...provides definitive evidence of intact adrenal function across all current diagnostic criteria 2, 1.