Endocrine Abstracts

Background: Investigating the origin of ACTH determine disparate treatment and prognosis in ACTH-dependent Cushing’s Syndrome. We want to detect the value of combination of HDDST and DDAVP stimulation test for identifying Cushing’s disease (CD) and Ectopic ACTH-dependent Cushing’s Syndrome (EAS).

Methods: We retrospectively recorded 102 ACTH-dependent Cushing’s Syndrome (87 CD and 15 EAS) in West China Hospital from January 1, 2010 to December 31, 2019. Focus on HDDST and DDAVP test, evaluated sensitivity (SE), specificity (SP) and cut-off obtained with ROC analysis respectively, estimate diagnostic accuracy when experiencing concordant tests.

Results: EAS patients have higher ACTH, serum cortisol, 24 h UFC levels, inversely weaker response to 1 mg dexamethasone suppression test (1 mg-DST) than CD (P < 0.01). As for HDDST, 24 hUFC suppression below 61.69% suggested a pituitary origin with a SE of 81% (95% CI : 70–90) and a SP of 79% (95% CI : 49–95). Suppressed series had lower baseline level compared with non-suppressed group (P < 0.01). A threshold percentage ACTH increase after DDAVP stimulation of 44.63% was able to identify CD with a SE of 91% (95% CI 83–97) and a SP of 80% (95% CI 52–96). When two parallel test results consistent, the diagnostic accuracy matched to BIPSS or pathology verification could reach 95.52%, up to 100% attached MRI ≥ 6 mm findings.

Conclusion: Combined with HDDST and DDAVP stimulation test can enhance accuracy rate searching origin of ACTH secretion, especially in cases with ≥ 6 mm MRI uncovering, BIPSS could be avoid.