Lowering cortisol enhances growth hormone response to growth hormone releasing hormone in healthy subjects.

Cortisol is known to influence growth hormone release probably by modulating somatostatin tone. We examined the effect of metyrapone (the 11 beta-hydroxylase inhibitor) treatment on growth hormone response to growth hormone releasing hormone (1 microgram kg-1 body wt). Six healthy male subjects were tested on two occasions 1 wk apart. On one occasion they received metyrapone followed by growth hormone releasing hormone and on the other placebo followed by growth hormone releasing hormone. In all subjects metyrapone produced a significant drop in cortisol levels. Together with this drop there was a significant enhancement of growth hormone response to growth hormone releasing hormone. The GH response was negatively correlated with the cortisol level. Growth hormone release in response to growth hormone releasing hormone challenge is thus seen to be heavily influenced by cortisol levels.