A novel tool in the diagnosis and follow-up of (cyclic) Cushing's syndrome: measurement of long-term cortisol in scalp hair.

BACKGROUND Measurement of cortisol in 24-h urine collections and midnight saliva are standard screening tests for Cushing's syndrome (CS). These tests reflect cortisol levels during a maximum of 24 h and do not provide historical information. Therefore, they can yield normal results in case of cyclic CS, which is a rare disorder that is characterized by alternating episodes of endogenous cortisol excess and normal cortisol secretion. The measurement of cortisol in scalp hair is a novel tool that might be helpful to establish the diagnosis of (cyclic) CS. Our aim was to study whether hair cortisol timelines correspond with clinical course in patients with CS and whether we could create retrospective timelines of cortisol exposure that correspond with symptomatic periods in patients suspected of cyclic CS. METHODS Scalp hair was collected in 14 patients with confirmed CS and six patients suspected of cyclic CS. Cortisol was extracted from the hair samples with methanol, and an ELISA was used to measure cortisol levels in hair extracts. A group of 96 nonobese individuals were used as a control group. RESULTS Hair cortisol levels were significantly elevated in CS patients (P<0.0001). Sensitivity and specificity of hair cortisol measurements for CS were 86 and 98%, respectively. Hair cortisol timelines of patients with CS and cyclic CS corresponded with clinical course. CONCLUSION Hair samples can provide a historical timeline that corresponds with clinical course in patients with (cyclic) CS. This new diagnostic tool can contribute significantly to early recognition of patients suffering from cyclic CS.