Diagnostic Tests for Addison's Disease
Addison's Disease: Diagnostic Tests
The list of diagnostic tests
mentioned in various sources as
used in the diagnosis of Addison's Disease
Home Diagnostic Testing
These home medical tests may be relevant to Addison's Disease:
Tests and diagnosis discussion for Addison's Disease:
A diagnosis of Addison's disease is made by biochemical laboratory
tests. The aim of these tests is first to determine whether there are
insufficient levels of cortisol and then to establish the cause. X-ray
exams of the adrenal and pituitary glands also are useful in helping to
establish the cause.
ACTH Stimulation Test
This is the most specific test for diagnosing
Addison's disease. In this test, blood and/or urine cortisol levels are
measured before and after a synthetic form of ACTH is given by injection.
In the so called short, or rapid, ACTH test, cortisol measurement 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 form of adrenal insufficiency
respond poorly or do not respond at all.
When the response to the short ACTH test is abnormal, a "long" ACTH
stimulation test is required to determine the cause of adrenal
insufficiency. In this test, synthetic ACTH is injected either
intravenously or intramuscularly over a 48- to 72-hour period, and blood
and/or urine cortisol are measured the day before and during the 2 to 3
days of the injection. Patients with primary adrenal insufficiency do not
produce cortisol during the 48- to 72-hour period; however, patients with
secondary adrenal insufficiency have adequate responses to the test on the
second or third day.
In patients suspected of having an addisonian crisis, the doctor must
begin treatment with injections of salt, fluids, and glucocorticoid
hormones immediately. Although a reliable diagnosis is not possible while
the patient is being treated, measurement of blood ACTH and cortisol
during the crisis and before glucocorticoids are given is sufficient to
make the diagnosis. Once the crisis is controlled and medication has been
stopped, the doctor will delay further testing for up to 1 month to obtain
an accurate diagnosis.
Insulin-Induced Hypoglycemia Test
A reliable test to determine how the
hypothalamus and pituitary and adrenal glands respond to stress is the
insulin-induced hypoglycemia test. In this test, blood is drawn to measure
the blood glucose and cortisol levels, followed by an injection of
fast-acting insulin. Blood glucose and cortisol levels are measured again
at 30, 45, and 90 minutes after the insulin injection. The normal response
is for blood glucose levels to fall and cortisol levels to rise.
Once a diagnosis of primary adrenal
insufficiency has been made, x-ray exams of the abdomen may be taken to
see if the adrenals have any signs of calcium deposits. Calcium deposits
may indicate TB. A tuberculin skin test also may be used.
If secondary adrenal insufficiency is the cause, doctors may use
different imaging tools to reveal the size and shape of the pituitary
gland. The most common is the CT scan, which produces a series of x-ray
pictures giving a cross-sectional image of a body part. The function of
the pituitary and its ability to produce other hormones also are tested.
(Source: excerpt from Addison's Disease: NIDDK)