Extraction and Analysis of Cortisol from Human and Monkey Hair

Abstract

The stress hormone cortisol (CORT) is slowly incorporated into the growing hair shaft of humans, nonhuman primates, and other mammals. We developed and validated a method for CORT extraction and analysis from rhesus monkey hair and subsequently adapted this method for use with human scalp hair. In contrast to CORT "point samples" obtained from plasma or saliva, hair CORT provides an integrated measure of hypothalamic-pituitary-adrenocortical (HPA) system activity, and thus physiological stress, during the period of hormone incorporation. Because human scalp hair grows at an average rate of 1 cm/month, CORT levels obtained from hair segments several cm in length can potentially serve as a biomarker of stress experienced over a number of months.In our method, each hair sample is first washed twice in isopropanol to remove any CORT from the outside of the hair shaft that has been deposited from sweat or sebum. After drying, the sample is ground to a fine powder to break up the hair's protein matrix and increase the surface area for extraction. CORT from the interior of the hair shaft is extracted into methanol, the methanol is evaporated, and the extract is reconstituted in assay buffer. Extracted CORT, along with standards and quality controls, is then analyzed by means of a sensitive and specific commercially available enzyme immunoassay (EIA) kit. Readout from the EIA is converted to pg CORT per mg powdered hair weight. This method has been used in our laboratory to analyze hair CORT in humans, several species of macaque monkeys, marmosets, dogs, and polar bears. Many studies both from our lab and from other research groups have demonstrated the broad applicability of hair CORT for assessing chronic stress exposure in natural as well as laboratory settings. Video LinkThe video component of this article can be found at

Relationships between affiliative social behavior and hair cortisol concentrations in semi-free ranging rhesus monkeys

“…Samples were stored in a foil pouch at −80°C until shipment to the Hormone Assay Core Laboratory at the University of Massachusetts Amherst. Following Meyer et al (2014), samples were weighed, washed twice with isopropanol and dried for 5–7 days under a fume hood. For all hair assays, we used the entire length of the shaved hair, as the founding study validating the hair cortisol assay in rhesus macaques found no significant difference in proximal versus distal hair segments when hair samples were divided in half (Davenport et al, 2006).…”

Chronic stress impacts the cardiovascular system: animal models and clinical outcomes

“…Diurnal variations are not applicable to this procedure, and cortisol levels are very stable in hair samples (226). On the other hand, there are some drawbacks; for example, the effects of short-lived stressors are difficult to detect using this technique.…”

Analysis of cortisol in dog hair - a potential biomarker of chronic stress: a review

“…It was suggested that structural damage of distal hair segments might have been caused by liquids like water and cosmetics (Kirschbaum et al 2009), or alcohol used to wash the samples before analysis (Manenschijn et al 2011). In monkey hair, the amount of cortisol remaining after washing was inversely related to the number of shampoo exposures (Meyer et al 2014). Assuming that hair in humans grows approximately 1 cm per month and that humans typically wash their hair at least several times per week, hair located several centimetres from the scalp might be exposed to over-shampooing, which appears to be a significant contributor to variation in cortisol levels (Meyer et al 2014).…”

“…In monkey hair, the amount of cortisol remaining after washing was inversely related to the number of shampoo exposures (Meyer et al 2014). Assuming that hair in humans grows approximately 1 cm per month and that humans typically wash their hair at least several times per week, hair located several centimetres from the scalp might be exposed to over-shampooing, which appears to be a significant contributor to variation in cortisol levels (Meyer et al 2014). Stalder and Kirschbaum (2012) suggested that frequent washing procedures may partially influence HCC in humans but it is unknown whether dogs are similarly affected.…”