Correspondence

Clinical Problem-Solving: Localizing the Source of Ectopic Corticotropin

N Engl J Med 1994; 331:814September 22, 1994

Article

To the Editor:

The differential diagnosis of corticotropin-dependent Cushing's syndrome and the localization of an ectopic source of corticotropin secretion are among the most difficult tasks in endocrinology. In his excellent discussion of the evaluation of an occult corticotropin-secreting tumor (May 5 issue),1 Dr. Kreisberg stops short of suggesting any further workup when conventional radiologic procedures (chest film, computed tomography [CT], and magnetic resonance imaging of both chest and abdomen) fail to detect the tumor.

In a recent series of 10 consecutive patients with ectopic corticotropin secretion, the source of the hormone remained obscure in 5 patients. As early as 1984, Segerson et al. localized the source of occult ectopic corticotropin secretion when chest radiography and chest CT failed to detect any abnormality by means of selective bronchial lavage2. Corticotropin levels in lavage fluid coming from the segmental bronchus of the left lower lobe were markedly elevated. Recently, Lamberts et al.3 successfully demonstrated tumors in three of five patients with occult ectopic corticotropin secretion, using somatostatin-receptor scintigraphy. Two of these patients had bronchial carcinoids that were later removed. In view of the known deficiencies of medical therapies for Cushing's syndrome and the potential hazards of bronchial carcinoids or islet-cell tumors, every attempt should be made to identify the source of corticotropin. Scintigraphy using octreotide labeled with indium-111 or iodine-123 seems to be a promising tool in the evaluation of such patients.

Przemyslaw Lastowiecki, M.D.
Northwestern University, Chicago, IL 60611

3 References

1. 1

   Kreisberg R. Half a loaf. N Engl J Med 1994;330:1295-1299
   Full Text | Web of Science | Medline

2. 2

   Segerson TP, Raff H, Katzoff MN, Levy SA, Findling JW. Intermittent ectopic Cushing's syndrome: localization of an occult ACTH source by selective bronchial lavage for ACTH. In: Endocrinology: proceedings of the 7th International Congress of Endocrinology, Quebec City, July 1-7, 1984. Amsterdam: Excerpta Medica, 1984:1395. abstract.
   

3. 3

   Lamberts SW, de Herder WW, Krenning EP, Reubi JC. A role of (labeled) somatostatin analogs in the differential diagnosis and treatment of Cushing's syndrome. J Clin Endocrinol Metab 1994;78:17-19
   CrossRef | Web of Science | Medline

Author/Editor Response

Dr. Kreisberg replies:

To the Editor: I appreciate the comments of Dr. Lastowiecki about the Clinical Problem-Solving case entitled “Half a Loaf” and the importance of locating the occult source of corticotropin production. I did not discuss bronchial lavage because the experience of Doppman with this technique was disappointing1. Saline lavage was negative in seven patients undergoing lobectomy for known corticotropin-secreting bronchial carcinoids1.

Recently de Herder et al. described their experience with somatostatin-receptor scintigraphy in 8 of 10 patients with ectopic tumors secreting corticotropin and corticotropin-releasing hormone or metastases of those tumors2. The technique frequently missed hepatic metastases and was actually negative in the only patient in whom the ectopic source of corticotropin or corticotropin-releasing hormone was truly occult. Eight of the 10 patients who had positive scans had extensive metastases that were easily detected by physical examination, radiologic techniques, surgery, or postmortem examination. The scintigraphy added little to their management and was actually unnecessary. Somatostatin-receptor scintigraphy was performed recently in the patient described in “Half a Loaf” and was negative.

Thus, neither lavage nor scintigraphy has yet proved useful. Even the investigators who developed somatostatin-receptor scintigraphy state that receptor negativity is common in patients with bronchial carcinoids3.

Robert A. Kreisberg, M.D.
University of Alabama, Birmingham, AL 35294

3 References

1. 1

   Doppman JL. The search for occult ectopic ACTH-producing tumors. Endocrinologist 1992;2:41-46
   CrossRef

2. 2

   de Herder WW, Krenning EP, Malchoff CD, et al. Somatostatin receptor scintigraphy: its value in tumor localization in patients with Cushing's syndrome caused by ectopic corticotropin or corticotropin-releasing hormone secretion. Am J Med 1994;96:305-312
   CrossRef | Web of Science | Medline

3. 3

   Lamberts SW, de Herder WW, Krenning EP, Reubi J-C. A role of (labeled) somatostatin analogs in the differential diagnosis and treatment of Cushing's syndrome. J Clin Endocrinol Metab 1994;78:17-19
   CrossRef | Web of Science | Medline

Citing Articles (1)

Citing Articles

1. 1

   W.W. de Herder, S.W.J. Lamberts. (1996) Is there a role for somatostatin and its analogs in Cushing's syndrome?. Metabolism 45, 83-85
   CrossRef