ABSTRACT
Bilateral inferior petrosal sinus sampling(IPSS) is known to be useful for the differential diagnosis of ACTH-dependent Cushing's syndrome and for the preoperative localization of pituitary microadenomas.To evaluate the usefulness of IPSS, we performed the procedure in the 17 cases of ACTH-dependent Cushing's syndrome including 2 cases of macroadenomas, 6 of them with CRH stimulation test. A inferior petrosal sinus-to-peripheral ACTH ratio of 2:1 or greater(3:1 after CRH stimulation) indicates a pituitary source of ACTH hypersecretion, and a ratio of the ACTH level in one inferior petrosal sinus to the ACTH level in the other of 1:4 or greater lateralizes the microadenomas to that half of the pituitary gland.With these criteria, we diagnosed Cushing's disease in 15 of 17 cases of ACTH-dependent Cushing's syndrome, and localized the lesion in 8 of 13 cases of microadenoma.In conclusion, IPSS with CRH stimulation has high diagnostic accuracy in the differential diagnosis of ACTH-dependent Cushing's syndrome, but still has the limitations on the localization of microadenoma.
