New method to measure cortisol could lead to better understanding of development of common diseases

Cortisol is a hormone produced by the adrenal glands and its primary role is to help maintain body metabolism. If the body is put under (psychological or physical) stress, cortisol levels increase to allow the body to respond to the situation. Currently the standard method to measure cortisol levels is to take a blood or saliva sample. However, since cortisol is released in a circadian rhythm and with pulses throughout the day, levels can fluctuate considerably, meaning it is difficult to estimate an individual's long-term exposure to cortisol through blood and saliva tests alone. Finding a new non-invasive method to measure long-term cortisol exposure could have a major impact on our ability to determine the role of cortisol in the development of many common diseases, such as cardiovascular disease, diabetes and depression.

Dr Laura Manenschijn and her team from Erasmus MC in The Netherlands collected scalp hair samples from 195 healthy individuals and from 11 patients with Cushing's syndrome (a condition where the adrenal glands produce too much cortisol) and 3 patients with Addison's disease (a condition where the adrenal glands are unable to produce cortisol) and tested their cortisol levels. All participants filled out a questionnaire to assess what products and treatments they used on their hair. A subset of 46 participants also had their waist and hip measurements taken.

The team found that hair cortisol levels correlated positively with waist to hip ratio (r=0.425, p=0.003) and waist circumference (r=0.392, p=0.007), meaning people with higher exposure to cortisol showed higher abdominal obesity. In individuals with Cushing's syndrome the levels of cortisol in hair were significantly higher than in healthy individuals (p<0.0001). In long hair of individuals with Cushing's syndrome and Addison's disease, the levels of hair cortisol corresponded with clinical records of the amount of cortisol they had been exposed to. Additionally, in long hair of healthy women, the team were able to record alterations in cortisol exposure due to psychological stress over time. Hair cortisol levels were not influenced by gender (p=0.353), hair colour (p=0.413), frequency of hair wash (p=0.673) or hair products (p=0.109), although there was a slight, borderline significant, decrease in cortisol levels in hair that was treated (dyed/bleached) (p=0.08).

This is the first time that cortisol measurements taken from hair have been shown to correlate with known tissue effects of cortisol, such as abdominal obesity, and to provide a retrospective timeline of exposure to this hormone. The next step is to use this technique in larger studies to examine the role of long-term cortisol exposure in the development of cardiovascular disease and depression. Ultimately, this could lead to a better classification of individuals at risk of common conditions and novel approaches to prevent these.

Researcher Dr Laura Manenschijn from Erasmus MC said: "We have suspected for a while that cortisol may be implicated in the development of many common conditions, such as heart disease, diabetes and depression. However, until now, doctors have not been able to accurately measure cortisol exposure over the long-term and so research into this has been limited.

"Our results are very exciting as they show that measuring the amount of cortisol in hair can potentially be used to monitor a person's long-term exposure to cortisol. This technique could lead to many potential uses in clinical research and has the additional benefit that it is easy to use and non-invasive.

"The results of this study show that hair cortisol is a reliable measure of long-term cortisol exposure. Now, we would like to use this tool in larger studies to examine the role of cortisol in the development of conditions such as cardiovascular disease and depression."