What Is the Best Sampling Region for Endocrine Hair Analysis? A Comparison Between the Posterior Vertex and Occipital Region and Recommendation for Standardization

This study investigated the optimal scalp region for endocrine hair analysis by comparing the posterior vertex and occipital region in 53 participants. Each participant provided 12 hair samples over two time points, and concentrations of various hormones and endocannabinoids were measured. The results showed no consistent differences between the two regions in terms of intra-region variability, test-retest correlations, and associations with external criteria. However, significant mean differences in analyte concentrations were found, with higher cortisol and cortisone in the occipital region and higher OEA, SEA, and PEA at the posterior vertex. The study emphasizes the need for standardized sampling practices and proposes anatomical landmarks for precise region localization.