Thesis Format

Integrated Article

Applications of Hair as a Record of Systemic Exposure to Cortisol

Jeffrey Matthew Levine, The University of Western OntarioFollow

Degree

Master of Science

Program

Physiology and Pharmacology

Supervisor

Rieder, Michael J.

Abstract

Hair cortisol content (HCC) is a novel biomarker that uniquely captures retrospective systemic cortisol exposure. This thesis aimed to assess how different hair growth rates effect HCC timelines in Cushing’s and Addison’s patients, investigate the relationship between HCC and age, puberty, sex and BMI in healthy children and adolescents, and assess novel methods to improve cortisol extraction and recovery. Retrospective HCC timelines derived from a 0.75 cm/month growth rate best matched 50% of patients’ medical records rather than the historically assumed 1 cm/month. HCC correlated positively with age (p<0.0001), puberty status (p<0.001), and BMI (p<0.01) in males and females 7-17 years old. Nitrogen evaporation resulted in greater cortisol recovery than air evaporation (p=0.0003), and hair digestion using NaOH resulted in more rapid extraction of cortisol. These results provide incremental improvements to previous methods and assumptions for HCC analysis and elucidate normal HCC changes in children and adolescents.

Summary for Lay Audience

Cortisol, the main glucocorticoid hormone in humans, is part of the normal stress response and has historically been assessed in serum, saliva, and urine. To generate long-term data from these acute measures, they must be repeatedly collected over time which is both invasive and costly. Cortisol in scalp hair has been growing in popularity as a less invasive, longer-term correlate of cortisol exposure. We retrospectively evaluated whether cortisol levels in hair correlated to reported symptomatology in the medical records of Cushing’s or Addison’s patients over months to years. Historical hair cortisol timelines generated by segmental hair analysis of these patients reflected reported changes in clinical states. In another study, we collected hair samples from a healthy cohort of 250 children and adolescents to assess hair cortisol changes with age, puberty status, BMI and sex. Hair cortisol increased with age, puberty status and BMI, but did not differ between sexes or correlate with age-adjusted BMI. In an effort to develop a high-throughput protocol for hair cortisol analysis we tried two methods of hair digestion. We assessed sodium hydroxide or enzymatic hair digestion to decrease extraction time and improve method reproducibility compared to the standard method which requires mincing with scissors and a 16-hour methanol extraction. We were unable to assay cortisol from the enzyme digests but were able to recover cortisol using sodium hydroxide digestion. When comparing two evaporation methods, we found that nitrogen evaporation is provides a better environment for hair cortisol recovery.

Recommended Citation

Levine, Jeffrey Matthew, "Applications of Hair as a Record of Systemic Exposure to Cortisol" (2019). Electronic Thesis and Dissertation Repository. 6647.
https://ir.lib.uwo.ca/etd/6647