"As a potential solution to the limitations of these tests, hair cortisol has been increasingly studied as an additional means to diagnose patients with Cushing Syndrome. Much like hemoglobin A1C is a longitudinal marker of blood glucose levels, hair cortisol can be a measure of the body's glucocorticoid levels over the previous several weeks to months."
Read more at https://cushieblog.com/2017/02/09/hair-test-for-cushing-syndrome/