Endocrine Abstracts

Objectives: To describe the results of the bilateral inferior petrosal sinus sampling (BIPSS) performed in our hospital for differential diagnosis between Cushing disease (CD) and ectopic ACTH secretion (EAS), and evaluate if CRH stimulation during this test improves its diagnostic accuracy.

Material and Methods: We retrospectively review 29 BIPSS performed in 26 patients (4 men, 22 women), with mean age of 44.7 year-old (range 28–69), diagnosed with ACTH-dependent Cushing´s syndrome and followed in the Endocrinology and Nutrition Department of La Paz University Hospital from 2001 to 2019. All BIPSS were performed using CRH stimulation; ACTH and prolactin levels were determined at baseline and three, six and ten minutes post-stimulation. A central-to-peripheral ACTH gradient ≥2.0 at baseline or ≥3.0 after CRH stimulation was the cut-off to diagnose CD and central-to-peripheral prolactin ratio ≥1.8 was considered successful catheterization of the inferior petrosal sinus (IPS). The gold standard to confirm CD was the histological finding of ACTH-secreting pituitary adenoma and/or remission after surgery.

Results: In 17 (58.6%) of the 29 BIPSS performed, both IPS were successfully catheterized, in 8 (27.6%) only the right was catheterized, in 3 (10.3%) it was only the left and in 1 (3.4%) no IPS was catheterized. Of the 28 BIPSS with at least one IPS correctly catheterized, 24 (85.7%) diagnosed CD; 21 of these patients went to surgery and only 8 (38.1%) had histology of ACTH-secreting pituitary adenoma, 10 patients had no pathological findings and the histopathology reports of the other patients were not found. All patients with histological findings of adenoma and other 5 patients without findings got into remission; therefore in 13 patients (61.9% of operated patients) CD was confirmed. The other patients underwent computed tomography and Octreoscan that did not show any tumor suggestive of EAS, so their diagnosis remains indeterminate. Three patients with positive BIPPS result are currently waiting for surgery. Among the 4 BIPSS that ruled out a pituitary ACTH hypersecretion, EAS was confirmed in 2 patients (3 BIPSS). All patients with a positive BIPSS result and diagnosis of CD confirmed by histology and/or remission, had baseline central-to-peripheral ACTH gradient >2.0 (sensitivity 100% at baseline), and >3.0 after CRH (sensitivity 100% post-stimulation).

Conclusion: BIPSS allowed a right diagnosis in the 100% of our patients with CD or EAS subsequently confirmed by histology and/or remission, being a very highly sensitivity test. CRH stimulation did not improve the sensitivity of BIPSS in our patients.