Long-term benzodiazepine administration blunts growth hormone response to diazepam

Growth hormone and prolactin responses to diazepam were measured in eight male patients who had been receiving long-term treatment with benzodiazepines and eight age-matched drug-free controls. The growth hormone response was significantly attenuated during benzodiazepine administration, but increased significantly after benzodiazepine treatment was discontinued. Growth hormone responses four days after the drug therapy withdrawal in patients, however, were still significantly less than in drug-free controls. Prolactin levels were unaltered after diazepam challenge, both in patients and in controls. The results clearly demonstrate tolerance to the growth hormone-releasing effect of diazepam, but do not suggest receptor supersensitivity after withdrawal of benzodiazepine therapy. It is possible that pituitary mammotropes lack benzodiazepine receptors.