Inferior petrosal sinus sampling in the diagnosis of adrenocorticotropin dependent Cushing syndrome with unknown origin

Objective: To evaluate the value of inferior petrosal sinus sampling (IPSS) in the diagnosis of adrenocorticotropic hormone (ACTH) dependent Cushing syndrome (CS) with unknown origin. Methods: IPSS was carried out for the diagnosis of 16 cases with ACTH dependent CS who had not been identified after a series of dexamethasone suppression tests and radiological examinations. The ratio of inferior petrosal sinus/peripheral ACTH was assayed. The sensitivity and specificity of diagnosis of the Cushing disease were estimated. Results: The inferior petrosal sinus/peripheral ACTH ratio was over 2.0 in 13 cases. Twelve cases underwent surgery with pathological diagnosis of pituitary ACTH adenoma, 1 patient relieved after γ knife treatment. The ratio was < 2.0 in 3 cases including 2 pulmonary carcinoid and one pituitary ACTH adenoma. The sensitivity and specify of IPSS for the diagnosis of Cushing disease were 13/14 and 2/2 respectively. Conclusion: IPSS was a safe technique with high sensitivity, specify and infrequent complications in the diagnosis of ACTH dependent Cushing disease. It had great clinical value in the differential diagnosis of ACTH dependent Cushing disease with unknown origin. (authors)