Endocrine Abstracts

Introduction: Inferior petrosal sinus sampling (IPSS) has been considered to be the gold standard for differential diagnosis of Cushing’s Disease (CD) and ectopic ACTH secretion (EAS).

Aim: To describe the experience of our centre in performing IPSS, its safety and efficacy; assess remission rates from transphenoidal surgery and clinical course; approach to the difficulty in the etiological diagnosis of ACTH-dependent Cushing’s Syndrome.

Methods: In this single centre retrospective study we included 14 patients diagnosed with ACTH-dependent Cushing’s Syndrome which IPSS were performed between 2011-2021. The diagnosis of CD was made when the basal central/peripheral ACTH ratio was> 2 and/or the rate after CRH/desmopressin stimulation was > 3. With the inter-sinus ratio> 1.3, lateralization was determined.

Results: 2 patients whose IPSS failed due to anatomical variation and vasovagal syncope were excluded. In 12 patients, 7 were female patients. Median age: 48.9 ±11.9 years. Sellar magnetic resonance imaging (MRI) demonstrated pituitary microadenoma in 10 cases. IPSS results were conclusive for diagnosis of CD in 83% of patients (10) and none of them indicated EAS. Lateralization by IPSS and MRI was concordant in 9 out of 10 cases with CD and microadenoma. Inconclusive results in 2 IPSS: 1) blood sample collection into non-EDTA tube; 2) absence of measurement of prolactin and impossibility of assessing correct sampling in the absence of basal central/peripheral ACTH ratio. In 10 of 12 patients whose IPSS showed CD diagnosis, correct lateralization was confirmed by the operation in one patient only. Pathology specimens did not show pituitary adenoma in the other 5 cases. The rate of remission after transsphenoidal surgery was 2 out 6 patients.

Conclusions: IPSS is a safe procedure and an effective test in the differential diagnosis of ACTH-dependent Cushing’s Syndrome. In our study, the sensibility of IPSS assessed was 83%, similar to what is described in the previous studies. DDaVP stimulation was equivalent to CRH stimulation. We emphasize the possibility of procedural failures that must be identified. It should be noted that regardless of whether or not there is a pituitary adenoma image on an MRI, IPSS proved to be useful to confirm CD and suggest a lateralization of ACTH secretion.