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

The study described a new assay for measuring cortisol in human hair, which was intended to serve as a biomarker for long-term systemic exposure. The researchers modified an existing immunoassay for saliva cortisol 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 dying after sample collection, but were decreased if the hair was dyed before sampling. The study reported a significant correlation between hair cortisol levels and 24-hour urine cortisol (r=0.33; P=0.041), supporting the use of hair cortisol as a biomarker for long-term cortisol exposure. The reference range for cortisol in hair was determined to be 17.7-153.2 pg/mg, with a median of 46.1 pg/mg.