Question: I am 4 years post pituitary Cushing’s and this year showed an elevated late night salivary cortisol. Are there things other than a recurrence of Cushing’s that could cause a high test result? Can you tell by how high the value is whether it is a recurrence?
 
Answer: First of all, most patients who have a recurrence of Cushing’s experience some symptoms such as mood changes, difficulty sleeping, possibly weight gain. A single night time salivary cortisol is not sufficient to diagnose a recurrence. The actual test level does not diagnose a recurrence. One consideration is the laboratory at which the test was conducted – not all labs are as accurate as others. Other things that can influence the test result include a change in the day/night sleep cycle, other illness, or significant stress.

The 3 tests that are screening tests for Cushing’s – the nighttime salivary cortisol test, the 1 mg overnight dexamethasone test and the 24 hour urine free cortisol test – have approximately the same accuracy: approximately 92% reliable. In order to determine if a patient has Cushing’s or a recurrence of Cushing’s the most important thing is to demonstrate CONSISTENT overproduction of cortisol. This may take several tests, so patience is needed. A single test is not adequate to determine if a patient has Cushing’s or recurrence of Cushing’s.

By Dr. Mary Lee Vance, University of Virginia, Charlottesville, VA,  Summer 2015