Intravenous infusion of beta-endorphin increases serum prolactin, but not growth hormone or cortisol, in depressed subjects and withdrawing methadone addicts.

In a randomized, double blind, cross-over study, human beta-endorphin or saline was infused iv over 30 min into six depressed psychiatric patients and four methadone addicts. All depressed subjects showed prompt, 2- to 4-fold increases in serum PRL levels, which lasted at least 2 h. The addicts, who were undergoing acute methadone withdrawal, showed similar PRL increases, which were dose dependent. beta-Endorphin did not increase serum levels of cortisol or GH in either group of subjects. These results suggest that iv beta-endorphin has potent but selective neuroendocrine effects in depressed patients and subjects withdrawing from methadone.