Hormonal effects of beta-receptor blockade during exercise

The effects of two different beta-receptor blocking agents, beta 1-selective metoprolol (150 mg/day) and non-selective propranolol (120 mg/day), on hormonal responses to physical exercise (30 min bicycle ergometer test) were compared with placebo within a double-blind, cross-over design in 7 healthy male volunteers. Plasma prolactin levels decreased from the initial values during and after exercise during treatments with placebo and beta-receptor blocking agents, but they were constantly higher with the two beta-blocking agents than with placebo. Exercise did not affect plasma testosterone levels, but during propranolol they remained higher than during placebo and metoprolol. The plasma LH and FSH levels were not affected by exercise, nor were they significantly modified by beta-blockade. The results of this study as well as those of previous studies indicate that beta-receptor blocking agents interfere with physiological endocrine functions and that the non-selective agents may have more distinct effects in this respect.