In humans and rhesus monkeys, dexamethasone decreased concentrations of plasma cortisol but did not alter circulating beta-endorphin immunoreactivity. Contrary to current theory suggesting that pituitary beta-endorphin and adrenocorticotropic hormone are controlled by identical regulatory mechanisms for synthesis and release, our evidence suggests that in higher primates the established glucocorticoid feedback mechanism for the adrenocorticotropic hormone-cortisol system does not regulate beta-endorphin secretion in the same way.

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