A Novel Tool in the Diagnosis and Follow-Up of (Cyclic) Cushing's Syndrome: Measurement of Long-Term Cortisol in Scalp Hair

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.