Intravenous Infusion of β-Endorphin Increases Serum Prolactin, but Not Growth Hormone or Cortisol, in Depressed Subjects and Withdrawing Methadone Addicts*

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Abstract
In a randomized, double blind, cross-over study, human β-endorphin or saline was infused iv over 30 min into six depressed psychiatric patients and four methadone addicts. All depressed subjects showed prompt, 2-to4-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.β-Endorphin did not increase serum levels of cortisol or GH in either group of subjects. These results suggest that iv β-endorphin has potent but selective neuroendocrine effects in depressed patients and subjects withdrawing from methadone.