The value of inferior petrosal sinus sampling in diagnosis and treatment of Cushing's disease

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Abstract
OBJECTIVE While microsurgical selective adenomectomy is the best method available at present for the treatment of Cushing's disease, its success depends to a large degree on precise preoperative intrapituitary microadenoma localization. This study compares the results of intrapituitary adenoma localization obtained with inferior petrosal sampling, computerized tomography and magnetic resonance imaging with the adenoma localization as found at surgery. DESIGN The results of inferior petrosal sampling for intrapituitary localization of ACTH-producing pituitary adenomas were compared in a retrospective study with the results of computerized tomography, magnetic resonance imaging, surgical and pathological findings. Special attention was paid to the intersinus ACTH relation. PATIENTS Thirty-eight patients (33 women and 5 men) of 11-68 years of age suffering from pituitary-dependent Cushing's disease were studied. Patients with ectopic ACTH-secreting tumours and and recurrent pituitary adenomas were excluded. MEASUREMENTS Blood samples were obtained simultaneously from both inferior petrosal sinuses and a peripheral vein before and 5, 10, 15 and 20 minutes after stimulation with 60 /μg/m2 human corticotrophin-releasing hormone (hCRH). RESULTS of the adenomas in our series, 42% had a diameter of 3 mm or less. Only 6 of 20 adenomas examined by computerized tomography and 11 of 29 examined by magnetic resonance imaging were identified correctly. Inferior petrosal sinus sampling produced significantly better results, particularly when combined with a stimulation test with hCRH: for 29 of 38 adenomas examined, the location was predicted correctly with these techniques. Analysis of the intersinus adrenocorticotrophin concentration ratio showed that the best right-central-left discrimination was obtained with values of 1.3 and 1.4. CONCLUSIONS We conclude that inferior petrosal sinus ACTH sampling after hCRH stimulation is the best method available for the intrapituitary localization of microadenomas causing Cushing's disease provided that the appropriate technique of blood sampling is used meticulously.