Plasma immunoreactive beta-endorphin in dexamethasone suppressors and non-suppressors of cortisol

Immunoreactive plasma beta-endorphin level was assayed in 33 patients with major affective disorder and in 16 psychiatrically normal controls before and after dexamethasone (1 mg) administration at 23.00 h. There were 18 cortisol suppressors and 15 non-suppressors among the patient group. All controls suppressed cortisol. Plasma beta-endorphin before dexamethasone was significantly different between suppressors, non-suppressors and controls (P less than 0.05, ANOVA). Concentrations of beta-endorphin were 4.7 +/- 0.7, 3.1 +/- 0.3 and 2.8 +/- 0.3 pmol/l for non-suppressors, suppressors and controls respectively. Following dexamethasone, beta-endorphin concentrations were again significantly different between groups (P less than 0.005, ANOVA). Concentrations were 4.6 +/- 0.7, 2.3 +/- 0.2 and 1.6 +/- 0.2 pmol/l for non-suppressors, suppressors and controls respectively. The implications of these findings are discussed.