Concomitant Suppression of Plasma ACTH- and β-Endorphin-Like Immunoreactivity by Cyproheptadine, Naloxone, and Somatostatin in the Ectopic ACTH Syndrome

Summary

Release of plasma ACTH- and β-endorphin (β-EP)-like immunoreactivity (LI) was studied in vivo in a patient with an ectopic ACTH-producing malignant thymoma. Administration of lysin vasopressin stimulated concomitant release of plasma ACTH- and β-EP-LI. Administration of Cyproheptadine, naloxone, and somatostatin significantly suppressed plasma levels of ACTH- and β-EP-LI, while saline infusion did not. Gel exclusion chromatography of the plasma extracts revealed that ACTH-LI consisted of two components, large and small molecular weight form, while β-EP-LI consisted of three components, large molecular weight, β-lipotropin-, and β-EP-sized form; each of these components was incompletely suppressed by somatostatin infusion. It is suggested that certain tumors may have acquired aberrant multiple receptors during malignant transformation which may lead to the paradoxical hormone response as demonstrated in this case.

Key-Words:

Ectopic ACTH Producing Tumor - Cyproheptadine - Naloxone - Somatostatin - Ectopic Multiple Receptors