Lesson of the week: Raised cortisol excretion rate in urine and contamination by topical steroids

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Abstract
Case reports Case 1—A 49 year old woman with type 2 diabetes mellitus, hypertension, and depression was referred for investigation of possible Cushing's syndrome. The history was of deteriorating control of glycaemia and blood pressure. Outpatient measurement of overnight urinary cortisol:creatinine ratios showed grossly raised values (mean 255 μmol cortisol/mol creatinine; range 15-1191; normal <25 μmol/mol creatinine). She was admitted and underwent a series of complex tests to define her Cushing's syndrome, all of which yielded normal results. Despite this, the urinary free cortisol excretion rate remained high (4365 nmol/24 hour; normal rate <250 nmol/24 hour). This pattern strongly suggested the presence of a factor interfering in the measurement of urinary free cortisol, which we confirmed using gas chromatography. This showed excipients consistent with the use of topical steroid cream. Further questioning of the patient revealed that she had been using an antifungal cream containing hydrocortisone (Canesten HC, Baypharm, Bayer, Berks) for vaginal candidiasis. Once this was stopped, urinary free cortisol excretion rates returned to normal (120 nmol/24 hour). Case 2—A 38 year old woman with type 2 diabetes, gross obesity, and facial plethora also underwent investigations for Cushing's syndrome. Overnight urinary cortisol:creatinine ratios were again moderately raised over a two month period (range 14 to 137 μmol/mol creatinine; normal <25 μmol/mol creatinine), but serum cortisol concentrations were within reference limits with a normal diurnal variation and a normal result of an overnight dexamethasone suppression test. Because of the similarity with case 1, the patient was interviewed and also admitted using Canesten HC cream on perineal and vaginal areas to treat candidiasis. After she discontinued this treatment, urinary cortisol:creatinine ratios returned to normal on all three occasions tested (5, 11, and 11 μmol/mol creatinine).