Dexamethasone Fails to Suppress β-Endorphin Plasma Concentrations in Humans and Rhesus Monkeys

Abstract
In humans and rhesus monkeys, dexamethasone decreased concentrations of plasma cortisol but did not alter circulating β-endorphin immunoreactivity. Contrary to current theory suggesting that pituitary β-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 β-endorphin secretion in the same way.