Segmental Hair Analysis - A Retrospective Testosterone Diary?

The study aimed to determine if segmental hair analysis could serve as a retrospective diary of testosterone levels by examining the stability of testosterone in hair as it grows. Seventy participants (30 men and 40 women) provided hair and saliva samples over three months. Hair samples were segmented and analyzed for testosterone using radioimmunoassay, while saliva samples were analyzed using ELISA. The study found that testosterone is somewhat conserved in hair segments over time (rho = 0.405–0.461, p < 0.001, n = 66–67), but identified three confounders: higher testosterone concentrations in distal segments, the effect of frequent hair washing in reducing testosterone in distal segments, and variability in hair growth rate affecting temporal resolution. Additionally, sex, natural hair color, and relationship status were significant factors influencing hair testosterone levels. The study concluded that for future research, repeated hair sampling near the roots may be more reliable than analyzing changes between proximal and distal segments within the same sample, and that hair testosterone analysis should be adjusted for sex and hair color.