ACTH Stimulation Test for Adrenal Insufficiency with Total Cortisol Levels

Assay for Cortisol:

Chemiluminescence immunoassay (CLIA) .

Precautions:

Cosyntropin is category C of pregnancy.

Interpretation:

Normal response: Peak stimulated cortisol value > 18 mcg/dl at 30 min [1, 2]. Most patients achieve higher cortisol levels at 60 min compared to 30 min value following 250 mcg cortrosyn administration [2]. Accordingly, a cut-off value of 18 mcg/dL at 60 min may be associated with an increased false positive result.

Caveats:

Taking oral estrogen may result in elevation of the total cortisol level due to increased corticosteroid binding globulin [3].
Patients with albumin < 2.5 gr/dL may have a low cortisol level [4].
Sensitivity for the test is limited in secondary adrenal insufficiency . Specificity is > 95 %, thus a positive cosyntropin test result substantially increases the likelihood that the patient has secondary adrenal insufficiency [5].