Selective Venous Sampling for ACTH in Cushing's Syndrome

Abstract

Selective venous catheterization and sampling for ACTH were performed in 6 patients with ACTH-secreting pituitary adenomas (Cushing''s disease) and 4 patients with occult ectopic ACTH-secreting neoplasms. In 5 patients with Cushing''s disease in whom the inferior petrosal sinus could be catheterized, ACTH levels were unequivocally > simultaneous peripheral values: The ratio was > 2.0, with a range of 2.2-16.7. The inferior petrosal sinus-to-peripheral ACTH ratio in 3 patients with ectopic ACTH secretion was < 1.5. In the 4th patient, an arteriovenous gradient of 6.8 was shown 2 yr before a bronchial carcinoid tumor was clinically apparent. Central-to-peripheral ACTH ratios at the level of the jugular bulb and jugular vein were not diagnostic. Selective venous ACTH sampling from the inferior petrosal sinus is apparently a reliable and useful aid in the differential diagnosis of Cushing''s syndrome when standard clinical and biochemical studies are inconclusive.