Catheterization of the petrosal sinus: possible advantage of desmopressin stimulation in Cushing disease.

Thediagnosis of Cushing syndrome can be challenging, particularly when bilateral inferior petrosal sinus sampling (BIPSS) is required to differentiate ectopic tumors from pituitary adrenocorticotropic hormone (ACTH)-releasing tumors. When corticotropin-releasing hormone (CRH) is used as a stimulus, a state of hypercortisolism is required to suppress CRH receptors in pituitary corticotrophs, preventing the release of ACTH by normal pituitary tissue. By contrast, desmopressin acts through vasopressin receptors that are preferentially expressed in ACTH-secreting pituitary tumors, suggesting potentially different physiological behaviors during stimulation. We present the case of a 26-year-old woman with ACTH-dependent Cushing's syndrome who underwent desmopressin-stimulated BIPSS. Hormone levels on the day of catheterization indicated eucortisolism; however, ACTH levels in the petrosal sinus confirmed the diagnosis of Cushing disease. Following transsphenoidal surgery, immunohistochemical analysis confirmed a corticotroph adenoma with positive Tpit and ACTH staining. We hypothesize that desmopressin stimulation during BIPSS may provide diagnostic information even in the absence of biochemical confirmation of hypercortisolism at the time of the procedure, because vasopressin receptors are expressed in pituitary corticotroph adenomas rather than in normal corticotroph cells. Further studies are needed to evaluate and confirm this hypothesis.