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November 17, 1993

Loperamide to Diagnose Cushing's Syndrome-Reply

JAMA. 1993;270(19):2302. doi:10.1001/jama.1993.03510190055023

In Reply.  —We have no personal experience with the loperamide test for the differential diagnosis of hypercortisolism described by Ambrosi and colleagues.1 Their recent article describes 58 patients in whom the diagnosis of Cushing's syndrome was entertained, 17 of whom had documented Cushing's syndrome. Ambrosi et al found the loperamide test equivalent to the 1-mg overnight dexamethasone suppression test in discriminating Cushing's syndrome from others. However, no information is given in this article regarding these patients' basal biochemical data. Thus, it is not clear that the patients who were excluded from the diagnosis of Cushing's syndrome had significant hypercortisolism. The patients with pseudo-Cushing's states described in our recent article2 were all selected for having urine-free cortisol excretion outside the normal range and for their failure to suppress cortisol following the 1-mg overnight dexamethasone test. Thus, it is unknown whether the loperamide test is of equal value for these