Endocrine Abstracts

Introduction: Inferior Petrosal Sinus Sampling (IPSS) is the gold standard test to distinguish between Cushing Disease and ectopic ACTH secretion (EAS), mostly when the biochemical tests are discordant and/or there is no lesion in MRI.

Aim: To evaluate the results of IPSS in the diagnosis of ACTH-dependent Cushing syndrome.

Methods: Retrospective study that analysed IPSS results performed in the last decade in our centre and integrated in the clinical context of each patient. Basal central-to-peripheral ratio>2 or after CRH test>3 were considered diagnostic of CD.

Results: We analysed 31IPSS performed in 26 patients with biochemical diagnosis of CS. Nine patients were excluded. Seventeen patients (2 Male) with a mean age of 38.4(11.8) years were included. One patient had to repeat IPSS due to haemolysis and other had done 3 IPSS due to be on interfering medication. Eleven patients had central-to-peripheral ACTH ratio suggestive of CD(6basal and 11after CRH stimulation). The ratio was maximal at 5′ in 45.4%(5/11) patients and at 2-3′ in 36.3%(4/11). Pituitary MRI revealed microadenoma in 8 patients, macroadenoma in one and 2 patients did not present any lesion. Three patients had a lesion on the other side of pituitary when compared to the intersinus gradient. Immunohistochemical result revealed an ACTH expression adenoma in 6 patients, and expression of ACTH and GH in 2. There was no positivity for ACTH in 3 patients who had MRI lesions, but one was cured after surgery and 2 underwent adjuvant therapy. Of the remaining 6 patients, 3 had results suggestive of ectopic EAS, one of which was submitted to lobectomy and had bilateral adrenalectomy by occult ectopic, but underwent pituitary surgery with a histological result revealing ACTH expression. Of the other 3 patients, all with pituitary MRI lesion, 2 patients underwent surgery that revealed CD and in the other the result was normal and patient underwent adrenalectomy. There were no significant adverse effects.

Conclusion: This study reinforces the utility of IPSS in identifying aetiology of SC, which was obtained in more than half of the patients, with no associated adverse effects. The IPPS catheterization was not possible in 1 patient.