Abstract
PurposeDynamic testing represents the mainstay in the differential diagnosis of ACTH-dependent Cushing’s syndrome. However, in case of undetectable or detectable lesion < 6 mm on MRI, bilateral inferior petrosal sinus sampling (BIPSS) is suggested by current guidelines. Aim of this study was to analyze the performance of CRH, desmopressin and high-dose dexamethasone suppression test (HDDST) in the differential diagnosis of ACTH-dependent Cushing’s syndrome as well as the impact of invasive and noninvasive tests on surgical outcome in patients affected by Cushing’s disease (CD).MethodsRetrospective analysis on 148 patients with CD and 26 patients with ectopic ACTH syndrome.ResultsAmong CD patients, negative MRI/lesion < 6 mm was detected in 97 patients (Group A); 29 had a 6–10 mm lesion (Group B) and 22 a macroadenoma (Group C). A positive response to CRH test, HDSST and desmopressin test was recorded in 89.4%, 91·4% and 70.1% of cases, respectively. Concordant positive response to both CRH/HDDST and CRH/desmopressin tests showed a positive predictive value of 100% for the diagnosis of CD. Among Group A patients with concordant CRH test and HDDST, no difference in surgical outcome was found between patients who performed BIPSS and those who did not (66.6% vs 70.4%, p = 0.78).ConclusionsCRH, desmopressin test and HDDST have high accuracy in the differential diagnosis of ACTH-dependent CS. In patients with microadenoma < 6 mm or non-visible lesion, a concordant positive response to noninvasive tests seems sufficient to diagnose CD, irrespective of MRI finding. In these patients, BIPSS should be reserved to discordant tests.
Highlights
Cushing’s syndrome (CS) is a rare and potentially fatal condition due to chronic exposure to cortisol
Among ACTH-dependent CS, the most common form is caused by an ACTH-secreting pituitary tumor, a condition named Cushing’s disease (CD), accounting for about 80% of all cases, whereas the rest is due to an ectopic source (EAS); even though ACTH levels are usually higher in ectopic ACTH syndrome (EAS) than in CD, there is a significant overlap between these two conditions, further diagnostic procedures are needed [1]
Previous studies found that the presence of concordant clear-cut response to both high-dose dexamethasone suppression test (HDDST) and corticotropin-releasing hormone (CRH) test is able to exclude the diagnosis of EAS, irrespective of magnetic resonance imaging (MRI) finding [8, 9]
Summary
Cushing’s syndrome (CS) is a rare and potentially fatal condition due to chronic exposure to cortisol. Given the fact that BIPSS is not 100% accurate, has poor reliability to suggest intrapituitary localization/lateralization and has some drawbacks [17], we collected clinical, biochemical and neuroradiological data of a large series of CD patients as well as biochemical and neuroradiological data of a group of EAS patients with the following aims: (i) to describe the responsiveness to dynamic testing (CRH test, DDAVP test and HDDST) and its performance in the differential diagnosis of ACTH-dependent Cushing’s syndrome in possible different scenarios given by MRI finding; (ii) to assess whether the decision of BIPSS execution can affect surgical outcome of patients affected by Cushing’s disease
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