Selective beta 1-adrenergic receptor-blockade with atenolol enhances growth hormone releasing hormone and mediated growth hormone release in man.

The growth hormone (GH) responses to a single bolus injection of the growth hormone releasing hormone (GRH) were examined in the basal state and in the presence of beta-adrenergic receptor blocking agents of different specificity in ten normal men. During a constant five-hour infusion of 56 micrograms/min of propranolol (nonselective beta-adrenergic receptor-blocker) in seven subjects studied, there was a significant augmentation of the GH release in response to exogenous GRH compared to the GH response during saline infusion, as measured by the peak serum GH concentrations after GRH (P = 0.019) and the integrated GH values (P = 0.019). A similar significant enhancement of GH responses to exogenous GRH as compared to the control day was observed with the specific beta 1-adrenergic receptor-blocker atenolol in all seven subjects studied (four of whom also participated in the propranolol study). Both the peak GH response to a GRH bolus and the integrated GH values were significantly greater with atenolol (P = 0.019 for both). There was no difference in serum GH concentrations after beta-adrenergic receptor-blocking drugs during a three-hour sampling period before GRH administration compared to placebo. Our results support the concept that beta-adrenergic receptors may modulate either the release or action of hypothalamic somatostatin in the control of GH secretion in man. We suggest the effect is mediated by specific beta 1-adrenergic receptors.