Study supporting DUTCH testing – Cortisol
by Mark Newman, MS
We have shared data before that shows a strong parallel between urine and saliva for free cortisol. In fairness, this data (from a study on Chronic Fatigue by Jerjes) did not show actual correlation data, and urine cortisol was plotted differently than what we do (total over time, not creatinine corrected). We have completed a small study that shows excellent correlation between saliva and urine for free cortisol (remember, our goal is to be at least “equivalent” to saliva testing for the free cortisol pattern and then improve the picture by adding in the cortisol metabolites and other markers unique to DUTCH) and we wanted to share it with you
Here’s what we did:
- Patients collected three saliva samples over a two hour period. At the end of this two hour period, a dried urine sample was collected.
- Samples were collected at various times and some with ACTH stimulation.
- Salivary free cortisol was tested by Rocky Mountain Analytical.
- Urinary free cortisol was tested by Precision Analytical.
- The three salivary results were added up and compared to the single urine sample that represented the same time period.
The correlation between the two measurements is terrific. In general, when free cortisol is low in saliva, you’ll find it low in DUTCH testing as well. From there your attention can move on Metabolized Cortisol. What we’ve found is interesting regarding the correlation between free cortisol and metabolized cortisol. You can see from the following data there is a GENERAL agreement between free cortisol levels and metabolized cortisol levels.
BUT…BUT…BUT…don’t miss this!… About 30% of people with low free cortisol overall, have elevated levels of metabolized cortisol. Think about the implications of that. When you see low overall free cortisol in saliva (or in urine) you THINK cortisol production is low. In almost one out of three patients, they are actually making more cortisol than 80% of their peers. They make lots of cortisol! You just can’t see it in the free cortisol. Obesity, hyperthyroid, long-term stress and other conditions drive up the metabolism/clearance of cortisol (resulting in high cortisol production and metabolites, but not high levels of free cortisol). Proper assessment of HPA-axis activity requires the free cortisol picture over time (diurnal rhythm) and the total of the metabolites (remember, free cortisol is only about 1% of the total and metabolites are >50% of the total). This is the #1 reason we developed this test. We wanted to give you the most comprehensive look at cortisol, and that’s exactly what DUTCH does!
Want more information on this new testing model? Listen to my chat with Dr. Kara Fitzgerald.