Salivary Cortisol Testing: Diagnosing Episodic Cushing’s Disease
Doctors use salivary testing to check for diurnal rhythm variations in hormones. While saliva doesn’t always match blood levels for every hormone, there is a very high correlation for cortisol. Our diurnal rhythm (inner clock) triggers the largest release of cortisol in the early morning to wake us up.
In patients with Cushing’s disease, this rhythm is inappropriately high in the evening. This alteration is a crucial piece of the puzzle in establishing a proper diagnosis.
What is Episodic Cushing’s Disease?
Dr. Friedman was one of the first endocrinologists to recognize that most Cushing’s patients are episodic (or periodic), meaning they have high cortisol values mixed with normal ones.
In his 2010 study published in Hormone and Metabolic Research, Dr. Friedman found that 65 out of 66 patients had at least one normal test despite having the disease. Therefore, multiple tests during a “high” are necessary for an accurate diagnosis. Late-night salivary cortisol testing (between 11 PM and midnight) is the most convenient way to capture these peaks.
Identifying a “High” Phase
To know when to test, look for these symptoms of elevated cortisol:
- Mental State: Wired at night, anxiety, irritability, euphoria, or “speed talking.”
- Physical Changes: Weight gain, water retention (edema), acne, or high blood pressure.
- Energy: Insomnia, or energy levels that “perk up” after sunset while tasks feel unusually easy.
Dr. Friedman recommends keeping a diary of your symptoms alongside each test to help identify your specific cycle.
Protocol for Collecting Saliva Samples
You must pick up a kit with salivettes (blue-top for Quest; white-top for LabCorp) from your local station.
Preparation (Both Labs)
- 24 Hours Before: Avoid steroid creams (hydrocortisone) or inhalers to prevent contamination.
- 60 Minutes Before: Do not brush or floss (to avoid bleeding gums).
- 30 Minutes Before: Do not eat or drink anything.
- 10 Minutes Before: Do not drink water.
- Timing: Collect between 11:00 PM and 12:30 AM.
Collection Procedure
- LabCorp: Place the cotton pad in your mouth and roll it for 90 seconds (or until saturated). Return the pad to the internal vessel and close firmly.
- Quest: Remove the swab and place it in your cheek for 2 minutes without chewing. Return the swab to the container.
Storage & Stability
- Refrigerated: Stable for 14 days (LabCorp) to 21 days (Quest).
- Frozen: Stable for 5 months (LabCorp) to 6 months (Quest).
- Note: You can freeze your samples and bring them to the lab together once you have completed the requested number of tests (usually 4).
Salivary Day Curves
In some cases, Dr. Friedman may request a Salivary Day Curve to monitor your circadian rhythm around the clock. This involves testing 8 times a day (8 AM, 11 AM, 2 PM, 5 PM, 8 PM, Midnight, 2 AM, and 4 AM).
He utilizes Quest or LabCorp for these curves, as home-directed tests like ZRT or non-FDA-approved options like eli.health are less reliable for medical diagnosis and insurance coverage.
Next Steps for Patients
If you are struggling with symptoms of Cushing’s Syndrome or need to schedule a consultation to review your salivary results, please visit our website.