Introduction: Cushings syndrome (CS) is certainly one of the most challenging disorders to physicians due to the difficulties that often appear during its investigation. The diagnosis of CS involves two steps: confirmation of hypercortisolism and determination of its etiology. Biochemical confirmation of the hypercortisolemic state must be established before any attempt for differential diagnosis. Failure to do so will result in misdiagnosis, inappropriate treatment, and poor management.
Objective: To assess the accurarcy of the various tests used in the diagnostic evaluation of endogenous CS.
Study design: A retrospective analysis of medical records was of patients with endogenous CS routinely followed in the Division of Endocrinology of Hospital das Clínicas, Federal University of Pernambuco, and in Pernambuco Endocrine Research Center, in Recife, northeast of Brazil, from January 2005 to December 2017.
Results: A total of 158 patients were enrolled: 99 (62.7%) with Cushings disease, 48 (30.4% with adrenal disorders), and 11 (6.9%) with ectopic ACTH secretion (EAS). Concerning diagnostic tests, serum cortisol (SC) levels ≥1.8 μg/dl after the 1mg overnight dexametahosne suppression test (1 mg-DST) were found in all but 10 patients (6.3%) who had cyclical hypercortisolism, whereas elevation of urinary free cortisol (UFC) and late-night salivary cortisol (LNSC) had sensitivites of 85% and 94%, respectively. Regarding tests used in the differential diagnosis of CS, ACTH levels were shown to be suppressed (<10 pg/ml) in all patients with adrenal adenomas or carcinomas, normal (40%) ou elevated (60%) in CD, and invariably high in cases of EAS. SC suppression >50% after the 8 mg overnight dexamethose suppression test (8 mg-HDDST) was encountered in 80% of patients of CD and in 27% of those with EAS. By contrast, SC suppression >80% were only seen in cases of CD (54% sensitivity). ACTH increase > 50% after desmopressin or CRH had 90% sensitivity and 90% specificity for CD. A positive response to both 8 mg-HDDST and desmopressin (or CRH) was only seen in subjects with CD. Magnetic resonance imaging (MRI) depicted adenomas in 65% of CD patients (19% with macroadenomas). Finally, bilateral inferior petrosal sinus sampling had a 94% accuracy in the diagnosis of CD.
Conclusion: In our cohort, 1 mg-DST and LNSC were the most accurate options to confirm hypercortisolism. Non-invasive dynamic tests have greater performance when performed in combination. However, SC suppression >80% after 8 mg-HDDST had 100% specificity for CD.
18 - 21 May 2019
European Society of Endocrinology