Dexamethasone Suppression Test- Why am I having this test?
Dexamethasone suppression test can be used to determine if your adrenal glands are overactive. If they are overactive, the test can also help your health care provider find the cause. This test can be used to help diagnose:
- Cushing syndrome.
- Cushing disease.
- Tumors of the adrenal gland or lung.
- Mental depression.
What is being tested?
This test looks at how your pituitary and adrenal glands are working together. It does this by measuring the level of a hormone called cortisol to determine your body’s response to a medicine (dexamethasone). You will be given this medicine for the test. The medicine normally leads to a reduced cortisol level. If it does not, this can indicate various conditions. There are two types of dexamethasone suppression tests: the prolonged test and the rapid test.
What kind of sample is taken?
The sample collected will depend on the kind of test that your health care provider chooses to perform:
- A prolonged test requires the collection of urine samples over a 24-hour period, in addition to blood samples.
- The rapid test requires a blood sample. It is usually collected by inserting a needle into a blood vessel.
Your health care provider will give you the instructions and supplies that you need for the test.
How do I collect samples at home?
You may be asked to collect urine samples at home over a certain period of time. Follow instructions from a health care provider about how to collect the samples.
When collecting a urine sample at home, make sure you:
- Use supplies and instructions that you received from the lab.
- Collect urine only in the germ-free (sterile) cup that you received from the lab.
- Do notlet any toilet paper or stool (feces) get into the cup.
- Refrigerate the sample until you can return it to the lab.
- Return the samples to the lab as instructed.
How do I prepare for this test?
- Follow your health care provider’s instructions. Your health care provider will give you instructions specific to the kind of test that will be done.
- Take
medicine only as told by your health care provider. For both the prolonged
and rapid tests, you will need to take a steroid medicine by mouth in
doses and timing that is determined by your health care provider.
- Take the medicine with food or milk to prevent stomach upset.
How are the results reported?
Your test results will be reported as levels of plasma cortisol. Your health care provider will compare your results to normal ranges that were established after testing a large group of people (reference ranges). Reference ranges may vary among labs and hospitals. For this test, common reference ranges are:
Prolonged test reference ranges
- Plasma cortisol: greater than 50% drop in your plasma cortisol is considered normal.
- Urine free cortisol in 24-hour collection: less than 20 micrograms (less than 50 nmol).
Rapid test reference ranges
- Plasma cortisol: less than 2 mcg/dL.
What do the results mean?
Values outside of the reference ranges may mean that your adrenal glands are overactive and that you may have:
- Cushing disease.
- Certain tumors that affect the adrenal gland or lung.
- Disorders of the adrenal gland.
- Mental depression.
Talk with your health care provider about what your results mean.
Questions to ask your health care provider
Ask your health care provider, or the department that is doing the test:
- When will my results be ready?
- How will I get my results?
- What are my treatment options?
- What other tests do I need?
- What are my next steps?
Summary
- The dexamethasone suppression test can be used to determine if your adrenal glands are overactive. If they are overactive, the test can also help your health care provider find the cause.
- This test looks at how your pituitary and adrenal glands are working together. It does this by measuring the level of a hormone called cortisol to determine your body’s response to a medicine (dexamethasone).
- Talk with your health care provider about what your results mean.
