Multiple forms of immunoreactive beta-endorphin are present in an ectopic adrenocorticotropin-producing tumor but not in normal pituitary or pituitary adenomas.

Human ACTH-producing tumor and plasma have been examined by gel filtration and ion exchange chromatography to detect the possible presence of reported multiple forms of immunoreactive beta-endorphin (I-EP) Ion exchange chromatography of I-EP obtained from gel filtration showed four components of I-EP [two major peaks in the positions of EP-(1-31) and EP-(1-27) and two minor peaks in the positions of N-acetyl EP-(1-31) and N-acetyl EP-(1-27)] in two ectopic ACTH-producing lung cancers, and two components of I-EP [the major peak in the position of EP-(1-31) and minor peak in the position of N-acetyl EP-(1-31) in an ectopic ACTH-producing thyroid cancer. Only a single peak in the position of EP-(1-31) was present in plasma from a patient with Nelson's sindrome and a patient with Addison's disease, in the pituitary adenomas from six patients with Cushing's disease, and in the nontumorous pituitary tissues from a patient with Cushing's disease and a patient with acromegaly. These data suggest that the posttranslational processing of EP in human pituitary is different from that in the ectopic ACTH-producing tumor.