Failure of naloxone to alter growth hormone and prolactin levels in acromegalic and in hyperprolactinaemic patients.

We examined the effects of high-dose intravenous naloxone administration in four acromegalic patients (mean serum growth hormone level 72 ng/ml) and in seven hyperprolactinaemic women (mean serum prolactin level 59 ng/ml), in order to assess whether this opiate antagonist would be effective in lowering growth hormone and prolactin levels. No effect was observed. This lack of effect suggests that an opioid pathway is not involved in the maintenance of elevated growth hormone or prolactin secretion in these patients. However, conclusions regarding the possible role of endogenous opioids in regulation of pituitary function in normal individuals cannot be drawn from this study.