Endocrine Abstracts

Introduction: Inferior petrosal sinus sampling for ACTH is the current gold standard test for the differentiation of pituitary Cushing disease from the ectopic ACTH syndrome. Early studies with İPSS reported a diagnostic sensitive and specificity approaching 100%, additional experience has shown a false negative rate of 1-10%. This has been due to either technical problem with unsuccessful petrosal sinus catheterization or anomalous venous drainage of the pituitary. The measurement of other anterior pituitary hormones may be useful during İPSS to improve the accuracy of the procedure.

Objective: The aim of the study is to increase the accuracy of the inferior petrosal sinus sampling procedure and reduce the false negative rate through the addition of prolactin as a marker of pituitary venous outflow as well as validate this adjunct to the test process.

Method: İn this retrospective cohort study, we reviewed 33 patients who had undergone IPSS for the investigation of ACTH dependent hypercortisolism at Marmara university hospital between 2011-2015. Plasma ACTH and Prolactin levels were measured both centrally and peripherally. The normalized ACTH/prolactin inferior petrosal sinus/peripheral ratio was then calculated to asses the accuracy of the sampling procedure.

Results: Thirty-three patients with confirmed ACTH dependent cortisol excess underwent investigation with İPSS. Thirty-two patients initially had a positive İPSS result (i.e. a basal central/peripheral ACTH ratio>2, and >3 post CRH). When the corrected prolactin data were used, one patient was additionally found to have positive result suggestive of pituitary Cushing’s. The prolactin normalized ACTH IPS/peripheral ratios were all >0.8 in patients proven Cushing’s disease.

Conclusion: Normalizing the İPS/peripheral ratios with prolactin helps to improve the accuracy of the results and reduces the false negative rate.