Diagnosis of cyclic Cushing syndrome using the morning urine free cortisol to creatinine ratio

Cortisol fluctuations in Cushing syndrome were first detected in 1956 and named cyclic Cushing syndrome [1]. Cycle lengths have been reported, varying between 12 hours and 85 days with at least three peaks and two troughs [2]. To assess cortisol production cycles, repeated hormone tests are necessary. According to the literature [2,3], tests to measure the early morning first-voided urine free cortisol to creatinine ratio (UFCCR) or salivary free cortisol can be used as feasible alternatives to assess cyclic cortisol overproduction because they are more convenient to perform. Here, we report a case of cyclic Cushing syndrome that was diagnosed using consecutive UFCCR, reported for the first time in Korea. KCI Citation Count: 1