Inferior petrosal sinus sampling (IPSS) to localize pituitarytumour in Cushing’s disease: its feasibility in Sri Lanka

A 27-year-old woman who remained undiagnosed regarding the source of hypercortisolism for four years was referred for further investigations. Initial laboratory results confirmed endogenous hypercortisolism, (elevated 9 a.m cortisol and non suppressible low dose dexa-methasone suppression test) suggesting Cushing’s syndrome. High dose dexamethasone suppression test did not suppress and serum adrenocorticotropic hormone (ACTH) level was elevated. MRI pituitary and CT abdomen, pelvis and chest also did not reveal any clue regarding the source of ACTH. Therefore venous sampling of Inferior-petrosalsinus and mediastinal vessels was arranged. In the unstimulated inferior- petrosal- sinus- sampling (IPSS), there was a central-to-peripheral ACTH gradient, of 2.6 times (higher in centre) and right to left gradient of 2.1 times (higher on right) were noted suggesting the right pituitary as source of excess ACTH. Repeat MRI pituitary revealed a 0.5cm x 0.3cm poorly enhanced area in the right lobe of suggesting a microadenoma. She underwent Trans Sphenoidal Surgery (TSS) and the histology appearances were compatible with a pituitary adenoma. Thisi case illustrates the feasibility of venous sampling in localizing the source of ACTH secretion where imagings were inconclusive.DOI: http://dx.doi.org/10.4038/sjdem.v1i1.4190  Sri Lanka Journal of Diabetes Endocrinology and Metabolism 2011; 1: 41-44