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Purpose: The differential diagnosis of adrenocorticotropic hormone (ACTH)-dependent Cushing's syndrome remains a challenge in clinical practice. The present study was aimed at assessing the diagnostic performance of pituitary dynamic contrast-enhanced magnetic resonance imaging (dMRI), high-dose dexamethasone suppression test (HDDST), and a combination of both tests for patients with ACTH-dependent Cushing's syndrome. Methods: A total of 119 consecutive patients with ACTH-dependent Cushing's syndrome confirmed surgically were enrolled: 101 with proven Cushing's disease and 18 with proven ectopic ACTH syndrome. All patients underwent pituitary dMRI and HDDST. The sensitivity and specificity of pituitary dMRI, HDDST, and a combination of both tests were determined. Results: The sensitivity and specificity of pituitary dMRI for diagnosing Cushing's disease were 80.2 and 83.3%, respectively, with a positive predictive value of 96.4%. The sensitivity and specificity of HDDST were 70.3 and 77.8%, respectively, with positive predictive value of 94.7%. A combination of both tests showed that the combined criteria of more than 50% suppression of serum cortisol on HDDST and a positive pituitary dMRI finding yielded a high specificity of 94.4 and sensitivity of 59.4%. The combined criteria of more than 68% suppression on HDDST and/or a positive pituitary dMRI finding yielded a sensitivity of 86.1% and specificity of 83.3%. Conclusions: Pituitary dMRI was superior to HDDST in the differential diagnosis of ACTH-dependent Cushing's syndrome. HDDST is recommended in combination with pituitary dMRI to establish a diagnosis process because of the significantly increased specificity with the combination. [ABSTRACT FROM AUTHOR]

Background: Definite diagnosis and treatment of Cushing's syndrome is still a dilemma. The aim of this study was to evaluate the accuracy of diagnostic tests and follow-up of patients with Cushing's syndrome."nMethods: Two hundred and fifty three consecutive cases with Cushing's syndrome during 1370-78 were studied. The screening tests were performed in all patients. High dose dexamethasone suppression test (HDDST) and ACTH measurement were carried out. MRI/CT Scan were performed and compared with laboratory data and pathologic specimens as a gold standard test."nResults: The age range was 32±11 yrs. The most frequent symptoms were weakness; hypertension, typical striae, and depression .The frequency of hypertension in ACTH-dependent case were 77% vs. 36% in adrenal tumors (P< 0.001). HDDST was positive in 99% of micro and 71% of macroadenomas. Adrenal tumors showed 3.6% suppression but none in ectopic cases. HDDST had a sensitivity of 98%, specificity of 97% and accuracy equals to 98%. The frequency of different etiologies was as following: Cushing's disease in 64.8%, adrenal tumors in 32.8% and ectopic ACTH in 2.4% of patients. Trans-sphenoidal surgery (TSS) was performed in 120 patients .The patients were followed for 53±25 months whose remission periods were 46.7±23.8 months (range 4-114 months). Survival analysis showed 93% remission rate in 12mo, 82% in 2yr and only 33% after 5yr.This recurrence didn't have any platue level."nConclusion: In our study, hypertension was more prevalent in ACTH-dependent Cushing's syndrome. HDDST had acceptable sensitivity, specificity and accuracy. Lifelong follow up of pituitary adenomas is inevitable in the case of progressive and gradual nature of recurrence in these tumors.