Cortisol, ACTH Stimulation

Serum

1.0 mL (each specimen)

0.7 mL (each specimen). (Note: This volume does not allow for repeat testing.)

Red-top tube or gel-barrier tube

Evaluation of possible primary and secondary adrenal insufficiency.^1-3,5

Pregnancy, contraceptives, and estrogen therapy can give rise to elevated cortisol concentrations. In samples from patients who have been treated with prednisolone,methylprednisolone, or prednisone, falsely elevated concentrations of cortisol may be determined due to cross-reactivity.⁶ Patients suffering from 21-hydroxylase-deficiency exhibit elevated 21-deoxycortisol levels, and this can also give rise to elevated cortisol levels.⁶ Severe stress can also give rise to elevated cortisol concentrations.⁶

As with all tests containing monoclonal antibodies, erroneous findings may be obtained from patients who have been treated with monoclonal mouse antibodies or who have received them for diagnostic purposes. In rare cases, interference due to extremely high titers of antibodies to streptavidin and ruthenium can occur. The test contains additives, which minimize these effects.

Electrochemiluminescence immunoassay (ECLIA)

The ACTH stimulation test (Cosyntropin) is used to assist in diagnosing primary and secondary adrenal insufficiency. Cosyntropin (ACTH 1-24) consists of the first 24 amino acids of the N-terminal portion of the intact native ACTH molecule (ACTH 1-36). It is the biologically active region of intact ACTH and is less allergenic than other forms of ACTH.^7,8 It acts rapidly when bound to the melanocortin-2 receptor (MC2R) of the adrenal cortex initiating synthesis and release of cortisol and its precursors. The magnitude and duration of response as measured by serum steroid levels may depend on the prior stimulation or suppression of the hypothalamic-pituitary-adrenal axis and the adequacy of drug administration.

Interpretation: A normal response is a rise from the baseline of cortisol, reaching at least 14.5 μg/dL 30 or 60-minutes post stimulation.⁹ A blunted or absent response suggests some level of adrenal insufficiency, cortical atrophy or significant suppression. Results should be interpreted within the context of patient’s medical history and clinical symptoms, particularly for patients with results near the cutoff.