Measurement of Cortisol in Human Hair as a Biomarker of Systemic Exposure

This study described a new assay for measuring cortisol in human hair, providing a non-invasive method to assess long-term cortisol exposure. The researchers modified an existing immunoassay for saliva to measure cortisol in hair and established a reference range for non-obese subjects. They found that hair cortisol levels were not affected by hair color or dyeing after sample collection, though dyeing before collection did decrease cortisol levels. The study reported a significant correlation between hair cortisol levels and 24-hour urine cortisol (r=0.33; P=0.041), supporting hair cortisol as a biomarker for long-term systemic exposure. The reference range for cortisol in hair was 17.7-153.2 pg/mg, with a median of 46.1 pg/mg.