Bilateral inferior petrosal sinus sampling using vasopressin

CONTEXT: Anatomical localization of pituitary adenoma can be challenging in adrenocorticotropic hormone (ACTH)-dependent Cushing's syndrome, and bilateral inferior petrosal sinus sampling (BIPSS) is considered gold standard in this regard. Stimulation using corticotrophin-releasing hormone (CRH) improves the sensitivity of BIPSS, however, same is not easily available in India. Therefore, we undertook this study of BIPPS using vasopressin as agent for stimulation owing to its ability to stimulate V3 receptors present on corticotrophs. AIMS: To study the tumor localization and lateralization in difficult to localize cases of ACTH-dependent Cushing's syndrome by bilateral inferior petrosal sinus sampling using vasopressin for corticotroph stimulation. SETTINGS AND DESIGN: Prospective observational study. SUBJECTS AND METHODS: Six patients (5 females) meeting inclusion criteria underwent BIPSS using vasopressin for stimulation. RESULTS: All six patients had nonsuppressible overnight and low dose dexamethasone suppression test with elevated plasma ACTH levels suggestive of ACTH-dependent Cushing's syndrome. High dose dexamethasone suppression test showed suppressible cortisol in two cases, and microadenoma was seen in two patients on magnetic resonance imaging pituitary. Contrast enhanced computed tomography of the abdomen showed left adrenal hyperplasia in one case and anterior mediastinal mass with bilateral adrenal hyperplasia another. Using BIPSS four patients were classified as having Cushing's disease that was confirmed histopathologically following surgery. Of the remaining two, one had primary pigmented nodular adrenocortical disease, and another had thymic carcinoid with ectopic ACTH production as the cause of Cushing's syndrome. No serious adverse events were noted. CONCLUSIONS: Vasopressin may be used instead of CRH and desmopressin for stimulation in BIPSS.