Inferior petrosal sinus sampling: Final solution to a riddle called "Cushing's syndrome"

Bilateral inferior petrosal sinus sampling (BIPSS) is gold standard test for anatomical localization for Cushing's disease.1 Initial reports on selective petrosal sinus sampling to differentiate pituitary and ectopic source of adrenocorticotropic hormone (ACTH) were performed by Corrigan published in 1977.2 Earlier, ratio of unilateral IPSS with peripheral venous ACTH levels was assessed but later on it was realized that pituitary venous drainage can be asymmetric either because of adenoma location or anatomical variation. Thus simultaneous BIPSS came into practice.3 In a meta-analysis of 21 studies, the overall sensitivity and specificity of BIPSS were found to be 96% and 100%4 respectively which can be improved after stimulation with CRH or desmopressin. Here we report a case of Cushing's disease with negative MRI brain for adenoma where BIPSS with stimulation with vasopressin confirmed the diagnosis and provided lateralization. She underwent successful surgical adenomectomy. Histopathology revealed pituitary adenoma and post operative cortisol level was consistent with remission.