Which diagnostic procedure is essential in confirming a diagnosis of adrenal insufficiency in a patient on long-term steroid therapy?

• A. 24-hour urine free cortisol test
• B. ACTH stimulation test
• C. Low-dose dexamethasone suppression test
• D. Corticotropin-releasing hormone test

Answer: (B)

The ACTH stimulation test is a key diagnostic procedure for confirming adrenal insufficiency, especially in patients who have been on long-term steroid therapy. In such cases, the suppression of the adrenal glands due to exogenous steroid use can lead to a secondary adrenal insufficiency. When administering ACTH (adrenocorticotropic hormone) to a patient suspected of having adrenal insufficiency, one would expect a normal adrenal gland to respond by producing cortisol.

If the adrenal glands are functioning correctly, there should be a significant increase in cortisol levels following the administration of ACTH. However, in a patient with adrenal insufficiency, particularly due to long-term steroid therapy, the adrenal glands may not respond adequately, indicating a problem with the adrenal axis and confirming the diagnosis.

The significance of this test lies in its ability to differentiate between primary and secondary adrenal insufficiency. In cases of primary insufficiency (like Addison's disease), the adrenal glands are damaged and cannot produce cortisol, whereas in secondary adrenal insufficiency (commonly seen in those on steroid therapy), the adrenal glands are intact but not activated properly due to the lack of ACTH stimulation from the pituitary.

In summary, the ACTH stimulation test plays a crucial role in assessing the functional capacity of the adrenal