Endocrine Abstracts

Introduction: The acute status of the hypothalamic-pituitary-adrenocortical (HPA) axis is routinely assessed by the measurements of cortisol in blood, saliva, and urine. Because cortisol is continuously deposited in the growing hair shaft, hair cortisol can serve as a practical measure of long-term retrospective HPA axis activity. The purpose of this review is to present the relevance of hair cortisol measurement in the diagnosis and management of Cushing’s syndrome and adrenal insufficiency.

Methods: A systematic search of literature was conducted using the search terms hair cortisol, Cushing’s syndrome, adrenal insufficiency, diagnosis, and management.

Results: Adult scalp hair grows at a rate of approximately 1 cm per month. A 1 cm of hair growth would represent total HPA axis activity of the previous 1 month. Therefore, the most proximal 1-cm hair cortisol is the best marker for the recent cortisol production. Longer hair samples can reflect cortisol production over months or years. For the measurement of hair cortisol, a 3-cm sample is taken from the posterior vertex of the scalp. If stored at room temperature and in intact hair, cortisol is stable for more than a year. Commercial kits (e.g., ELISA) can be used for the measurement of hair cortisol. The natural color of hair does not impact hair cortisol levels but excessive shampooing, hair dying, and prolonged exposure to UV light can diminish the cortisol levels. Obviously, baldness prevents the hair collection for cortisol measurement. Hair cortisol can be used as an initial or supportive diagnostic test for Cushing’s syndrome with high sensitivity and specificity. The most proximal 1-cm hair cortisol is the best marker of hypercortisolemia. Hair cortisol measurement also helps assessing the natural history of hypercortisolism and adrenal insufficiency by estimating the duration of the disease before diagnosis. Hair cortisol levels may also be useful in the monitoring of disease progression and treatment efficacy of adrenal disorders. However, since hair cortisol levels are not sensitive to the circadian fluctuations of cortisol, they cannot replace blood and salivary cortisol measurements.

Conclusion: Hair cortisol measurement is a new non-invasive approach to assess long-term retrospective HPA axis activity when diagnosing adrenal disorders. The most proximal 1-cm hair cortisol is the best marker of hypercortisolemia and can be used as an initial diagnostic test for Cushing’s syndrome. Hair cortisol is also useful in monitoring disease progression and treatment efficacy of adrenal disorders.