From the Guidelines
Adrenal insufficiency (Addison's disease) can be diagnosed using a combination of clinical suspicion, laboratory tests, and imaging studies. The diagnostic tests for adrenal insufficiency include:
- Paired measurement of serum cortisol and plasma ACTH to confirm the diagnosis of primary adrenal insufficiency (PAI) 1
- Synacthen (tetracosactide) stimulated test with a peak serum cortisol <500 nmol L-1 to diagnose PAI 1
- Low-dose or high-dose ACTH stimulation test to evaluate adrenal function, with the high-dose test being easier to perform and safe 1
- Basic metabolic panel to evaluate electrolyte levels, such as sodium, potassium, and glucose 1
- Renin and aldosterone levels to assess mineralocorticoid function 1
- Adrenal CT to evaluate for metastasis, hemorrhage, or other adrenal pathology 1
- Evaluation of ACTH and cortisol levels in the morning to assess adrenal function, with levels <3 mg/dL indicating potential adrenal insufficiency 1
In cases of suspected acute adrenal insufficiency, treatment should not be delayed by diagnostic procedures, and serum cortisol <250 nmol L-1 and increased ACTH can be diagnostic of primary PAI 1. The choice of diagnostic test may depend on the clinical context and the availability of resources.
From the Research
Diagnostic Tests for Adrenal Insufficiency
The diagnosis of adrenal insufficiency (Addison's disease) is based on clinical assessment and biochemical tests, including:
- Basal hormone level measurements
- Stimulation tests, such as the cosyntropin stimulation test 2, 3, 4, 5
- Assessment of cortisol level at 8am and ACTH level 4
- Insulin hypoglycemia test or metyrapone (Metopirone®) test if the Synacthen test is inconclusive 4
Specific Diagnostic Tests
- The cosyntropin stimulation test is the initial endocrine evaluation of suspected primary or secondary adrenal insufficiency 5
- The Synacthen test can give a false normal result in cases of pituitary origin for the deficiency, and alternative tests such as the insulin hypoglycemia test or metyrapone test may be necessary 4
- Magnetic resonance imaging of the brain may be performed to exclude the presence of a sellar or suprasellar mass 6
Interpretation of Test Results
- Low plasma cortisol and normal to low plasma ACTH indicates a pituitary origin for the deficiency 4
- The operating characteristics of the 250-microg and 1-microg cosyntropin tests are similar, but the lower sensitivity in patients with secondary adrenal insufficiency necessitates use of tests involving stimulation of the hypothalamus if the pretest probability is sufficiently high 5
- The diagnosis of secondary adrenal insufficiency may be challenging, and the therapy of adrenal insufficiency should be carefully tailored to the requirements of the individual patient 6