Simultaneous and bilateral catheterization of inferior petrosal sinuses in the diagnosis of Cushing's syndrome: basal multiple sampling and after ACTH-releasing hormone test]

In 22 patients with ACTH-dependent Cushing's syndrome we have performed multiple ACTH evaluations, baseline and after ACTH-releasing hormone (CRH), during simultaneous bilateral inferior petrosal sinus sampling. The basal inferior petrosal sinus/periphery ratio for ACTH was > 2 in 11/22 patients, CRH challenge caused the appearance of an inferior petrosal sinus/periphery ratio > 3 in 6 other patients. An ACTH-secreting adenoma was surgically proven in 17 patients with ACTH inferior petrosal sinus/periphery ratio > 2 basally or > 3 after CRH and in 1 patient with an inferior petrosal sinus/periphery ratio < 2 basally or 3 after CRH. In 4 patients the very high peripheral ACTH levels, the inferior petrosal sinus/periphery ratio and the lack of ACTH increase after CRH indicated the presence of an ectopic ACTH syndrome. An ACTH intersinus gradient > 1.4 was found in 11 patients. Among these patients the adenoma was correctly localised in 6 and wrongly in 5 patients. In conclusion, the diagnostic accuracy of the inferior petrosal sinus sampling was of 95.4% (21/22 cases) considering basal and CRH-stimulated ACTH levels. The multiple basal ACTH evaluation does not seem to be necessary associated with CRH-test, but may be helpful in some cases.