Bilateral inferior petrosal sinus sampling

Abstract

Simultaneous bilateral inferior petrosal sinus sampling (BIPSS) plays a crucial role in the diagnostic work-up of Cushing's syndrome. It is the most accurate procedure in the differential diagnosis of hypercortisolism of pituitary or ectopic origin, as compared with clinical, biochemical and imaging analyses, with a sensitivity and specificity of 88-100% and 67-100%, respectively. In the setting of hypercortisolemia, ACTH levels obtained from venous drainage of the pituitary are expected to be higher than the levels of peripheral blood, thus suggesting pituitary ACTH excess as the cause of hypercortisolism. Direct stimulation of the pituitary corticotroph with corticotrophin-releasing hormone enhances the sensitivity of the procedure. The procedure must be undertaken in the presence of hypercortisolemia, which suppresses both the basal and stimulated secretory activity of normal corticotrophic cells: ACTH measured in the sinus is, therefore, the result of the secretory activity of the tumor tissue. The poor accuracy in lateralization of BIPSS (positive predictive value of 50-70%) makes interpetrosal ACTH gradient alone not sufficient for the localization of the tumor. An accurate exploration of the gland is recommended if a tumor is not found in the predicted area. Despite the fact that BIPSS is an invasive procedure, the occurrence of adverse events is extremely rare, particularly if it is performed by experienced operators in referral centres.

Keywords: ACTH; Cushing’s syndrome; adrenal; petrosal sinus sampling; pituitary.

Figure 1

Algorithm representing authors’ current practice on the indication for BIPPS. CRH +: positive response to CRH stimulation test defined as an increment ≥30% of serum cortisol over baseline or ≥50% or more of plasma ACTH over baseline. CRH −: negative response to CRH stimulation test defined as an increment <30% of serum cortisol over baseline or <50% of plasma ACTH over baseline. *Use of BIPPS controversial, see text.

Figure 2

(A) Plasma ACTH concentration (pg/mL) in a patient with final diagnosis of Cushing’s disease (example of BIPSS data from the authors’ series). (B) Plasma ACTH concentration (pg/mL) in a patient with final diagnosis of EAS due to bronchial carcinoid (example of BIPSS data from the authors’ series).