In trying to diagnose Addison’s disease (also known as primary adrenal insufficiency), your doctor (or endocrinologist, if you’ve gone to a doctor who specializes in the endocrine system) may run several exams and tests. This will help the doctor narrow down your condition to Addison’s disease; in the early stages, Addison’s symptoms may be confused with other disorders.
To begin the diagnostic process, your doctor will perform a physical examination that includes a thorough review of your medical and family history. Then he or she will probably move on to laboratory and imaging tests.
Baseline Laboratory Testing
The first step if your doctor suspects abnormal adrenal function may be to measure your cortisol and ACTH levels. ACTH is the acronym for adrenocorticotropin hormone. ACTH is necessary to tell the adrenal glands to produce cortisol and other hormones. Cortisol levels follow a natural cycle throughout the day; they are highest in the morning, so most likely your doctor will want to draw these labs around 8 am.
ACTH Stimulation Test: Used to Diagnose Primary Adrenal Insufficiency
To begin the ACTH stimulation test, your doctor will draw some blood and measure the cortisol level. At the same time, he or she will probably measure your ACTH level. Next, cosyntropin (a synthetic derivative of ACTH) is injected, and then the doctor will draw your blood again to re-evaluate your cortisol level. Usually, the doctor checks your level twice: 30 and 60 minutes after the injection.
A normal response after cosyntropin injection is an increased cortisol level.
Most cases of primary adrenal insufficiency (Addison’s disease) can be diagnosed using the baseline lab tests and the ACTH test. Rarely difficult cases require additional testing using either the insulin tolerance test or the CRH stimulation test.
Insulin Tolerance Test: Used to Diagnose Primary and Secondary Adrenal Insufficiency
This test is considered the “gold standard” test for diagnosing adrenal insufficiency. However, it is potentially dangerous and only should be performed by experienced physicians (usually endocrinologists). It is considered unsafe to perform this test on people with ischemic heart disease or epilepsy. In addition, if your baseline cortisol is very low, this test should be avoided, as it could trigger an Addisonian crisis.
Your doctor will draw some blood to measure the cortisol level. Next, insulin is injected in order to lower your blood glucose. Blood will be drawn periodically to measure cortisol as your glucose level drops. Low blood glucose is a powerful stimulus to the pituitary to make ACTH, which leads to high cortisol levels. Sweating, rapid heart beat, and hunger are normal responses to low glucose. Once your sugar drops sufficiently and your blood is collected, the test is stopped by feeding you juice and snacks.
CRH Stimulation Test
CRH is the acronym for corticotropin-releasing hormone. CRH causes the pituitary gland
to secrete ACTH, which in turn causes the adrenal glands
to secrete cortisol.
To begin the CRH stimulation test, your doctor will draw some blood and measure the cortisol level. Next, synthetic CRH is injected into your bloodstream. Blood cortisol is measured every 30 minutes for about an hour and a half after the injection.
Possible CRH stimulation test results:
- If CRH injection causes an ACTH response, but no cortisol response, the pituitary is functioning but the adrenal glands are not. Such results are consistent with the diagnosis of primary adrenal insufficiency or Addison’s disease.
- If CRH injection does not generate ACTH response, the problem is the pituitary gland (secondary adrenal insufficiency).
- CRH injection produces a delayed ACTH response, the problem is the hypothalamus.
Imaging Tests: CT and MRI Scans
CT scans of your abdomen and MRI scans of your brain provide your doctor with a picture of your adrenal and pituitary glands. He or she can see the shape and size of each gland and determine if their appearance is normal or if something may be wrong.
The imaging tests listed above can support a diagnosis of adrenal insufficiency, but your doctor shouldn’t definitively diagnose the disorder from the tests. The hormone tests are what make the diagnosis, but imaging tests can provide further supporting information.