In its early stages, adrenal insufficiency can be difficult to diagnose. A review of a patient’s medical history and symptoms may lead a doctor to suspect Addison’s disease.
A diagnosis of adrenal insufficiency is confirmed through laboratory tests. The aim of these tests is first to determine whether levels of cortisol are insufficient and then to establish the cause. Radiologic exams of the adrenal and pituitary glands also are useful in helping to establish the cause.
ACTH Stimulation Test
The ACTH stimulation test is the most commonly used 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 given by injection. The normal response after an ACTH injection is a rise in blood and urine cortisol levels. People with Addison’s disease or long-standing secondary adrenal insufficiency have little or no increase in cortisol levels.
Both low- and high-dose ACTH stimulation tests may be used depending on the suspected cause of adrenal insufficiency. For example, if secondary adrenal insufficiency is mild or of recent onset, the adrenal glands may still respond to ACTH because they have not yet atrophied. Some studies suggest a low dose—1 microgram—may be more effective in detecting secondary adrenal insufficiency because the low dose is still enough to raise cortisol levels in healthy people but not in people with mild or recent secondary adrenal insufficiency.
CRH Stimulation Test
When the response to the ACTH test is abnormal, a CRH stimulation test can help 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 respond by producing high levels of ACTH but no cortisol. People with secondary adrenal insufficiency have absent or delayed ACTH responses. CRH will not stimulate ACTH secretion if the pituitary is damaged, so an absent ACTH response points to the pituitary as the cause. A delayed ACTH response points to the hypothalamus as the cause.
Diagnosis during an Emergency
In patients suspected of having an Addisonian crisis, health professionals must begin treatment with injections of salt, glucose-containing fluids, and glucocorticoid hormones immediately. Although a reliable diagnosis is not possible during crisis treatment, measurement of blood ACTH and cortisol during the crisis—before glucocorticoids are given—is enough to make a preliminary diagnosis. Low blood sodium, low blood glucose, and high blood potassium are also usually present at the time of an adrenal crisis. Once the crisis is controlled, an ACTH stimulation test can be performed to obtain the specific diagnosis. More complex laboratory tests are sometimes used if the diagnosis remains unclear.
Once a diagnosis of Addison’s disease is made, radiologic studies such as an x ray or an ultrasound of the abdomen may be taken to see if the adrenals have any signs of calcium deposits. Calcium deposits may indicate bleeding in the adrenal gland or TB, for which a tuberculin skin test also may be used. Blood tests can detect antibodies associated with autoimmune Addison’s disease.
If secondary adrenal insufficiency is diagnosed, doctors may use different imaging tools to reveal the size and shape of the pituitary gland. The most common is the computerized tomography (CT) scan, which produces a series of x-ray pictures giving cro...
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