Tests you should ask your doctor about if you suspect Cushing’s

by Kristin

Do you have symptoms of Cushing’s syndrome and feel like you’ve reached a dead end with your doctor because you don’t know what tests to ask for? Unless you’re lucky enough to be working with a doctor who’s familiar with recognizing the symptoms associated with Cushing’s and has had experience diagnosing Cushing’s, your doctor may or may not pursue the all tests necessary to confirm or deny a diagnosis of Cushing’s syndrome.

More often than not, testing for Cushing’s isn’t an open and shut case. It usually takes a combination of tests, with some of them being repeated more than once because levels can vary depending on the time of day or where a patient is in their cycle. Plus, not every patient will test positive on every single test. Everyone’s body is different and individual normal levels will vary. Some patients will present with off the charts levels of cortisol and it’s an obvious red flag, while others will present with the high end of normal to slightly elevated and both patients can be equally as sick. So if Cushing’s is suspected, it’s important to not let one single test or one negative test result close the case. If your doctor refuses to continue testing after only one test or a single negative test result, do yourself a favor and find a doctor who will. It’s your doctor’s job to help you get to the root of what’s making you sick. You can find a list of patient recommended doctors who specialized in diagnosing and treating Cushing’s syndrome here.

The most common test doctors will start with to screen for Cushing’s is to administer a 24-hour urine collection for urinary free cortisol excretion. There are some drawbacks with the test though. A large percentage of people with Cushing’s will have elevated levels of urine free cortisol, but some Cushing’s patients don’t test high and will actually have normal levels of urine free cortisol.¹ So it’s important to not use the 24-hour urine collection as the only determining factor to screen for Cushing’s.

Another widely used test for screening for Cushing’s is the low-dose dexamethasone suppression test. A synthetic steroid is administered that is supposed to suppress cortisol production to very low levels. For a majority of patients with Cushing’s, cortisol levels won’t drop. But there’s a small percentage of patients with mild Cushing’s and as a result their cortisol levels will be suppressed, resulting in a negative test.

The late night salivary cortisol test is considered one of the most sensitive screening tests for Cushing’s. Elevated cortisol between 11:00 p.m. and midnight appears to be the earliest detectable abnormality in patients with this disorder. Cortisol secretion is usually very low at this time of the day, but in patients with Cushing’s syndrome, the value is virtually always elevated. Although this is a relatively new test, it is currently the most widely studied single test for the diagnosis of Cushing’s syndrome with at least eight independent studies from all over the world demonstrating sensitivity of 93-100% for the diagnosis of Cushing’s syndrome.² The salivary cortisol test can be administered by your local hospital or can be completed with an at home kit. You can ask your doctor about which option is best for you & your needs.

If the results still prove to inconclusive, the dexamethasone CRH test can be helpful because some patients have high levels of cortisol but don’t develop the full-blown effects of Cushing’s syndrome. These patients may have pseudo-Cushing’s syndrome, a condition sometimes found in people who have depression or anxiety disorders, drink excess alcohol, have poorly controlled diabetes, or are severely obese. The dexamethasone-CRH test can distinguishes pseudo-Cushing’s from mild cases of Cushing’s.³

I know many of you have come across this information while searching for information about Cushing’s online and if you’re not familiar with the various tests, it can be overwhelming. I’ve provided links with additional information for all the tests I mentioned and hope it helps you to navigate the options & process of testing for Cushing’s syndrome.