From the Guidelines
Low ACTH and cortisol results on a dexamethasone stress test suggest adrenal insufficiency, which requires prompt medical attention, and treatment should be initiated with hydrocortisone (15-25 mg daily in divided doses) or prednisone (5-7.5 mg daily) as recommended by the ASCO guideline update 1. This condition occurs when your adrenal glands cannot produce adequate cortisol, a hormone essential for stress response, metabolism, and immune function. The low ACTH level indicates secondary adrenal insufficiency, meaning the problem likely originates in the pituitary gland rather than the adrenal glands themselves. This distinction is important for treatment planning, as primary and secondary adrenal insufficiency can be distinguished by the relationship between ACTH and cortisol, and management is as per hypophysitis in section 4.3 for secondary (central) adrenal insufficiency 1. You'll need to carry a medical alert card or bracelet, learn to adjust medication during illness or stress, and have an emergency injection kit containing hydrocortisone for severe situations. Regular follow-up appointments will be necessary to monitor your condition and adjust medication as needed, and endocrine consultation should be part of planning before surgery or high-stress treatments 1. It's also important to note that using hydrocortisone allows for recreation of the diurnal rhythm of cortisol, and typically, 2/3 of the dose is given in the morning and 1/3 in the early afternoon 1. Additionally, all patients need education on stress dosing for sick days, use of emergency steroid injectables, when to seek medical attention for impending adrenal crisis, and a medical alert bracelet for adrenal insufficiency to trigger stress dose corticosteroids by emergency medical personnel 1. In acute situations, stress dosing may be required (2-3 times the maintenance dose), and maintenance therapy should be adjusted based on volume status, sodium level, and renin response (target upper half of the reference range) 1. It's crucial to be aware of the need to start corticosteroids first when planning hormone replacement therapy for multiple deficiencies, as other hormones accelerate the clearance of cortisol and can precipitate adrenal crisis 1. Overall, the management of adrenal insufficiency requires careful consideration of the underlying cause, treatment planning, and patient education to prevent complications and ensure optimal outcomes.
From the Research
Dexamethasone Stress Test Results
- Low ACTH and cortisol levels can indicate adrenal insufficiency, a condition where the adrenal glands do not produce enough cortisol and aldosterone hormones 2, 3.
- The dexamethasone suppression test is used to diagnose adrenal insufficiency, and low ACTH and cortisol levels after the test can confirm the diagnosis 4.
- However, the test results should be interpreted with caution, as low cortisol levels can also be caused by other factors, such as septic shock or critical illness 2, 3.
Diagnostic Criteria
- The normal cortisol response to ACTH stimulation is considered to be ≥18 μg/dL (500 nmol/L), but newer specific cortisol assays may have lower thresholds for a normal response 5.
- A baseline cortisol level <2 μg/dL can be predictive of subnormal stimulated cortisol values, and a new serum cortisol cutoff of 14 to 15 μg/dL may be recommended depending on the assay used 5.
- The ACTH stimulation test is the most commonly used test to diagnose adrenal insufficiency, but the high-dose test is preferred over the low-dose test due to its higher sensitivity and specificity 2.
Treatment Options
- Hydrocortisone is the preferred corticosteroid for patients with septic shock and adrenal insufficiency, and it should be started as early as possible 2, 3.
- Fludrocortisone can be added on a case-by-case basis in refractory shock, but its use is controversial and requires further investigation 3, 6.
- Modern hydrocortisone replacement regimens may be associated with an increased risk of adrenal crisis, and further research is needed to determine the optimal treatment approach 6.