Adrenal Insufficiency Testing: An Introduction
Because symptoms of the condition occur gradually, it can be difficult to make an
adrenal insufficiency diagnosis. After asking a number of questions and performing a physical exam, the doctor may recommend certain tests as part of adrenal insufficiency testing. These adrenal insufficiency tests can include:
- ACTH (adrenocorticotropic hormone) stimulation test
- CRH (corticotropin-releasing hormone) stimulation test
- ACTH and cortisol blood levels
- Imaging tests.
Adrenal Insufficiency Testing: ACTH Stimulation Test
The ACTH stimulation test is the most specific test for
diagnosing adrenal insufficiency. In this test, blood cortisol, urine cortisol, or both are measured before and after a synthetic form of ACTH is administered by injection.
In the so-called short, or rapid, ACTH test, measurement of cortisol in blood is repeated 30 to 60 minutes after an intravenous ACTH injection. The normal response after an injection of ACTH is a rise in blood and urine cortisol levels. Patients with either type of adrenal insufficiency respond poorly or do not respond at all.
Adrenal Insufficiency Testing: CRH Stimulation Test
When the response to the short ACTH test is abnormal, a "long" CRH stimulation test is required to determine the cause of adrenal insufficiency. In this test, synthetic CRH is injected intravenously and blood cortisol is measured before and 30, 60, 90, and 120 minutes after the injection.
People with
Addison's disease (
primary adrenal insufficiency) have high ACTHs, but they do not produce cortisol. People with secondary adrenal insufficiency have deficient cortisol responses, but absent or delayed ACTH responses. Absent ACTH response points to the pituitary as the cause; a delayed ACTH response points to the hypothalamus as the cause.
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