Do Follicles Matter? Testing the Effect of Follicles on Hair Cortisol Levels

The study on 30 Scandinavian brown bears found that hair cortisol concentration (HCC) was significantly higher in samples with follicles, with a 6.6% increase compared to those without. This indicated that follicles could influence HCC, potentially due to residual blood or cortisol production within the follicle. The study highlighted the importance of standardizing hair collection and preparation methods to ensure valid comparisons across studies. Additionally, it noted that HCC varied with age and sex, increasing in older female bears but decreasing in males, with the follicle effect diminishing with age. The review of 77 papers reinforced the need for standardized guidelines in hormonal analyses using hair.