Bilateral inferior petrosal sinus sampling in the differential diagnosis of adrenocorticotropin-dependent Cushing's syndrome with unknown origin

Objective To evaluate the value of inferior petrosal sinus sampling in ACTH-dependent Cushing's syndrome with unknown origin.Method IPSS was carried out for the diagnosis of 20 cases of ACTH dependent Cushing's syndrome who had not been identified of diagnosis after a series of dexamethasone suppression tests and radiological examinations from Jan,2008 to Jan 2009.The ratio of plasma ACTH concentration between inferior petrosal sinus and peripheral veins was assayed.The sensitivity and specificity of diagnosis of the Cushing's disease were estimated.Results The basal ratio of ACTH concentration between inferior petrosal sinus and peripheral veins was ＞2 in 18 cases.13 cases underwent transphenoidal surgery with pathological diagnosis of pituitary ACTH adenoma;1 patient chose γ knife treatment and 4 patients chose somatostatin therapy with relieve of the disease.The basal ratio of ACTH concentration between inferior petrosal sinus and peripheral veins was ＜2 in 2 cases. One pulmonary node was removed by surgery with pathological diagnosis of carcinoid in 1 patient.One transphenoidal surgery was still undergone according to the clinical features in the other patient with pathological diagnosis of pituitary ACTH adenoma. The sensitivity and specify of inferior petrosal sinus sampling for the diagnosis of Cushing's disease in this study were 93% and 100% respectively.Conclusion Inferior petrosal sinus sampling is a safe technique with infrequent complications. It has great value in the differential diagnosis of ACTH-dependent Cushing's disease with unknown origin. Key words: Cushing's syndrome;  Cushing's disease;  Ectopic ACTH syndrome;  Inferior petrosal sinus sampling