Simultaneous measurement of beta-endorphin, lipotrophins and met-enkephalin in phaeochromocytomas.

Tissue concentrations of immunoreactive lipotrophin, beta-endorphin, and met-enkephalin were determined in 10 phaeochromocytomas, 3 of which were responsible for the ectopic ACTH syndrome. Lipotrophin and beta-endorphin immunoreactivities could be detected in all cases, whether or not Cushing's syndrome was present, and their tissue concentrations were significantly correlated (r = 0.95, P less than 0.001). Chromatographic studies showed that gamma-lipotrophin and beta-endorphin were the main peptides in the tumours. Met-enkephalin immunoreactivity was also found in all tumours examined, at much higher concentration and showing no correlation with either lipotrophin or beta-endorphin immunoreactivity. Although beta-endorphin and met-enkephalin are thought to originate from different precursor molecules, these data show that the two opioid peptides may be secreted by the same tumour. The evidence for excess secretion of opioid peptides and their pathological significance in phaeochromocytomas remain to be established.