Endocrine Abstracts

Purpose: Inferior petrosal sinus sampling (IPSS) is considered the gold standard test for the differential diagnosis of ACTH-dependent Cushing’s syndrome, but false-negative results have been reported in 1–10% cases. Cavernous sinus sampling (CSS) was suggested as a diagnostic tool in a complex ACTH-dependent Cushing’s syndrome cases.

Aim: To study the role of bilateral combined cavernous and inferior petrosal sinus sampling (BCIPSS) in differential diagnosis of ACTH-dependent Cushing’s syndrome.

Materials and methods: 34 patients (6 men) mean age 42,2±12,9(25–67) with ACTH-dependent Cushing’s syndrome were included. ACTH-dependent hypercorticism was diagnosed according to generally accepted recommendations. Indications for BCIPSS were: MRI pituitary adenoma size <8 mm in 26 cases or absence of pituitary tumor in 8 cases. ACTH CS(IPS)/P ratio≥2 or normalized ACTH/prolactin CS(IPS)/P basal ratio≥0,8 indicated the Cushing disease (CD). Ectopic ACTH-dependent syndrome (EAS) was diagnosed if ACTH CS(IPS)/P ratio was<2 or normalized ACTH/prolactin CS/P and IPS/P basal ratio was<0,6. All patients underwent surgery (transsphenoidal endoscopic adenomectomy in patients with CD, resection of ectopic ACTH-producing tumor in patients with EAS). Diagnosis CD or EAS was approved by immunohistochemistry and/or clinical improvement (adrenal insufficiency after operation).

Results: In 28 patients ACTH CS(IPS)/P ratio was≥2, that confirmed pituitary origin. Noteworthy, in two patients the data for CD were obtained only by the results of CS sampling, and in four only by the data of the IPS sampling. All patients underwent TSS, CD diagnosis after surgery was confirmed in everyone. In 6 patients ACTH CS(IPS)/P ratio indicated EAS: it was<2. But in three of them normalized ACTH/prolactin CS(IPS)/P basal ratio was≥0,8; also, they harbored an adenoma according to pituitary MRI. CD considered confirmed and TSS was performed in these three patients and subsequent IHC study confirmed the ACTH-secreting adenoma. In two patients the normalized ACTH/prolactin CS/P and IPS/P basal ratio was<0.6, in one 0.7. A survey to identify the source of ectopic ACTH-production was done. In one case it was pheochromocytoma with ectopic ACTH-secretion and in two cases bronchial carcinoid. All patients were successfully operated on.

Conclusion: According to our data, in the differential diagnostic of ACTH-dependent Cushing’s syndrome combined CS and IPS sampling may improve the results and increase the accuracy of the method. In ambiguous cases normalized ACTH/prolactin CS(IPS)/P basal ratio can be effectively used.