Acute and long-term effects of octreotide in patients with ACTH-dependent Cushing's syndrome

Octreotide is of proven efficacy in the management of patients with acromegaly, thyrotropin-secreting pituitary adenomas, and certain gastrointestinal tumors, but its effect in Cushing's syndrome is less clear.

We studied 10 patients who presented with adrenocorticotropic hormone (ACTH)-dependent Cushing's syndrome, 3 of whom were previously adrenalectomized. Serum cortisol or ACTH levels were measured before and during the administration of octreotide 50 to 500 micrograms every 8 hours for 24 to 72 hours.

Treatment was effective in four patients: serum cortisol levels decreased to within or below the normal range in Patients 1, 2, and 3, and ACTH levels were substantially lowered in Patient 4, who had previously been adrenalectomized for a metastatic islet cell tumor. These responses were sustained during long-term treatment for 2 to 72 weeks. All four patients showed no evidence of a pituitary tumor on computed tomographic or magnetic resonance imaging and had proven (Patients 3 and 4) or presumed ectopic disease. Of the six patients who did not respond, four had pituitary tumors and two had presumed ectopic ACTH production.

We conclude that a short trial of octreotide is warranted in patients with ACTH-dependent Cushing's syndrome who have no demonstrable pituitary tumor. A response to treatment should alert the physician to the possibility of an ectopic ACTH source and will identify patients whose disease may be controllable using octreotide.