Iatrogenic Cushing syndrome in 24-hour urine free cortisol measurement.

Cushing syndrome (CS) is caused by an excess of glucocorticoids that results in a variety of symptoms such as central obesity, moon facies, hirsutism, and reddish-purple stretch marks. Cortisol is the most potent endogenous glucocorticoid, and measuring the total amount excreted in the urine over a 24-hour period is useful to screen for CS caused by a tumor. However, most cases of CS are believed to be caused by exogenous glucocorticoids, such as prednisone and prednisolone, which are administered for anti-inflammatory and immunosuppressive treatments. This is often referred to as iatrogenic (drug-related or exogenous) CS. We modified an LC-MS/MS method for urine free cortisol to detect the presence of prednisone and prednisolone in patient samples. We wanted to understand the potential prevalence of exogenous CS in our patient population.