Summary: Improved testing methods are resulting in updates to the reference ranges for Metabolized Cortisol. These new ranges result in almost no change to current interpretation, and old and new reports can still be easily compared. Read the full article to understand the details below. 

At DUTCH, we are continually looking for ways to improve our testing methods so providers can have the greatest confidence in the results they use to guide patient care. As part of that commitment, on August 23, 2026, we are updating the reference ranges for the cortisol metabolites reported on the DUTCH test, including: 

• alpha-tetrahydrocortisol (a-THF) 
• beta-tetrahydrocortisol (b-THF) 
• beta-tetrahydrocortisone (b-THE)

These metabolites are found on page 5 of the DUTCH Complete and DUTCH Plus tests, seen below (example male): 

These metabolites are used in the following results:

• Metabolized Cortisol (The total of the three metabolites) 
• The Cortisol Clearance Rate (CCR) 
• The Systemic Preference 

All three of these calculated values are displayed in the graphics on page 4 of the DUTCH Complete and DUTCH Plus tests, shown to the rightà  

Why Are the Cortisol Metabolite Reference Ranges Changing? 

Reference ranges are established in the context of specific lab methods, or everything the lab does to measure an analyte.  

At DUTCH, one of our core values is "Always Advancing”, meaning we are always looking for ways to improve our testing methods and our products. As part of this, we have implemented methodological improvements in testing. Some of these improvements allow for better recovery of cortisol metabolites from patient samples. In practical terms, this means we capture more of the metabolites that are present in the sample, which has increased the reference range on some analytes. Other changes we implemented allow for more precise, and therefore more reproducible, results, which in some cases will have the net effect of lowering a range. 

With every method change made, we ALWAYS test thousands of patients to ensure the reference range is appropriate and accurate for both male and female patients, for each and every test.  

To account for these improvements, we have established updated reference ranges: 

Please note that while the female a-THF range increased, the female b-THF decreased in such a way that the total Metabolized Cortisol reference range, shown in the dial, did not change.  

What Will Providers Notice? 

The most noticeable change may be the numerical values themselves. However, because many providers use the arrows on our dials to review results, some may not notice the numbers. Comparing the arrows on the dials will not change. This is because the metabolite results are shown on a dial, with an arrow indicating where the patient falls within the reference distribution. As the reference ranges have been updated alongside the methodology, the percentile ranking will remain largely unchanged even when the numerical value differs. 

Male Example

If the same sample were analyzed using both the previous and updated methods, the result (numerical value) reported for a cortisol metabolite would be higher using the new method because recovery has improved. However, the patient's relative position within the reference population will remain the same.  

In other words, while the reported number may change, the clinical interpretation of where the patient falls relative to the population should remain consistent. This makes visually comparing older reports to new reports easy! 

Impact on Cortisol Metabolism Calculations

The cortisol metabolites are used to calculate the Cortisol Clearance Rate and the Systemic Preference. These calculations are presented as percentiles within the reference distribution. These calculations, which are explained in the sections below, have also been updated, but the take-home message is that there will be no difference in how the percentiles are read and interpreted.  

Impact on Cortisol Clearance Rate 

The Cortisol Clearance Rate will also use the new Metabolized Cortisol range, which estimates how rapidly cortisol is metabolized. It is calculated using: 

THF + THE / Cortisol + Cortisone

Because Metabolized Cortisol is part of the calculation, changes in metabolite recovery naturally affect the underlying numerical inputs. However, Cortisol Clearance Rate is reported as a percentile, which will not change.  

Impact on the Systemic Preference Slider

The Systemic Preference slider also uses the new Metabolized Cortisol range, which estimates the systemic balance of circulating cortisol versus cortisone using their metabolites. It is calculated as: 

(a-THF + b-THF) ÷ b-THE

Like Cortisol Clearance Rate, Systemic Preference is reported as a percentile, which will not change.  

One more time: Can Providers Still Compare New Reports to Older Reports? 

Yes! 

Historical results remain valid and clinically useful. The new methodology simply provides more complete recovery of cortisol metabolites and allows us to further improve analytical performance. 

Continuing Our Commitment to Better Testing 

At DUTCH, Always Advancing means continually refining our science so we can provide the most accurate and actionable insights possible. We are excited to bring these improvements to our providers while maintaining the consistency and reliability that have always been central to DUTCH testing.