Correlation of Cortisol in 1-Cm Hair Segment with Salivary Cortisol in Humans: Hair Cortisol as an Endogenous Biomarker

The study validated the correlation between cortisol levels in 1-cm hair segments and salivary cortisol in healthy humans, confirming that hair cortisol can serve as an endogenous biomarker for long-term hypothalamo-pituitary-adrenal activity. Salivary cortisol levels were collected at three different times and compared with hair cortisol levels measured 4 weeks later. Significant correlations were found between salivary cortisol at different times and between hair cortisol and average salivary cortisol, supporting the hypothesis that blood-related diffusion is a biologically endogenous source of hair cortisol.